No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Cuprophilic and ?-stacking interactions in the formation of supramolecular stacks from dicoordinate organocopper complexes
Abstract
The unsupported organocopper pyridine complexes C6F5Cu(py) (2) and [C6F5Cu]2(4,4'-bipy) (3) form supramolecular structures that are unprecedented in organocopper chemistry; one-dimensional chains of copper atoms with Cu...Cu distances of 2.8924(3) angstroms in the blue-luminescent complex are likely associated with cuprophilic interactions, whereas multiple perfluoroarene-arene interactions dominate in the supramolecular assembly of 3.
... Unlike crystal 2 with the ligands in a staggered conformation, both the polymorphs 3-a and 3-b show supramolecular two-dimensional stacks as a result of multiple perfluoroarene-arene p-interactions. Besides, the cuprophilic interactions may also exist in the two polymorphs and influence the charge transport properties [26]. To the best our knowledge, no theoretical study on the charge transport properties of polymorphs involving multiple intermolecular interactions has been reported in the literature. ...
... Å , and a = b = c = 90°and for 3-b, a = 9.288 Å , b = 5.033 Å , c = 22.316 Å , and a = c=90°, b = 92.57° [26]. Integrations over the Brillouin zone were sampled by 6 9 4 9 1 k points for 3-a and 4 9 8 9 2 k points for 3-b, using the Monkhorst-Pack scheme [33]. ...
... Jäkle and co-workers designed and synthesized the two polymorphs of [C 6 F 5 Cu] 2 (4,4 0 -bipy) with slow diffusion of a solution of 4,4 0 -bipyridine in CH 2 Cl 2 into a solution of [C 6 F 5 Cu] 4 , which are described in detail in Ref [26]. Figure 1 displays a graphical representation of the molecular structure and packing mode of the two polymorphs, 3-a and 3-b. ...
Due to the different molecular stacking conformations, two kinds of intermolecular interactions, arene–arene π-stacking interaction
and Cu–Cu interaction coexist in the polymorphs of [C6F5Cu]2(4,4′-bipy) crystals, 3-α and 3-β. However, the relative magnitude of the two kinds of intermolecular interactions in 3-α and 3-β is different. With the help of first-principle band structure calculations, the relationship between the charge transport abilities and
the intermolecular interactions in the two polymorphs was investigated for the first time. The analysis of band structures
and Г point wave functions of the band-edge state in the valence band of crystal 3-α shows that the Cu–Cu interaction so-called cuprophilic interaction determines the hole transport ability, although this interaction
is weaker than that in crystal 2 of C6F5Cu(py) discussed in our previous work, which is a promising hole transport material. For polymorph crystal 3-β, the wave functions of LUMO are mainly localized on the bipyridine (bpy) groups, which are result from the arene–arene π-stacking
interaction between the bpy groups. Such a π–π stacking interaction dominates the electron transport ability in the conduction
band of 3-β and makes the electron main carrier for transporting. The results are also supported by the analysis of effective masses
and density of states (DOS). Thus, the charge transport properties are dominated by different intermolecular interactions
due to the different molecule stacking in the two polymorphs.
... Alternatively, great attention was increased to the fact that clusters can be formed in Group II metals which in most cases exhibit short metal-metal distances [60]. The Cu I -Cu I closedshell interactions (CSIs) were early proved by extended calculations of Huckel which suggested the effects of hybridization of filled (n-1) d-orbitals and the ns and np orbitals [61][62][63][64][65]. The word "coprophilicity" was used to represent the Cu I -Cu I bonding interaction [62]. ...
The coordination polymer {[Cu6(CN)6]·HPD}n, CP1; (HPD = heptane‐1,7‐diamine) was prepared and characterized by single‐crystal and powder X‐ray diffraction, UV–Vis spectroscopy, electron microscopy (TEM and SEM), and elemental analyses. The copper atoms are coordinated by C ≡ N ligands, and both exhibit tetrahedral geometry. Cu1 and Cu2 create the pretty unique cluster structure of two quadruple [Cu2(μ³‐CN)2] units exhibiting coprophilic interaction. The building blocks [Cu3(CN)3]2 form fused distorted rectangular rings surrounded with the [Cu2(μ³‐CN)2] motifs exhibiting wide voids to accommodate the guest HPD. The structure of 1 indicates the formation of channels with dimensions 5.121–8.469 Ǻ which extend three‐dimensionally creating fused cavity morphology with different shapes. CP1 was utilized as an efficient sensor for selective quantitative estimation of metal ions (Co²⁺) and explosives (NB). Advanced oxidation process (AOP) was used as an efficient photocatalyst for the removal of the antibiotic meloxicam (MEL) utilizing AOP in the presence of H2O2 as an oxidant. Scavenge experiments, reusability of catalyst 1, and mechanism of oxidation were also discussed.
... The Cu1···Cu2′ distance of 2.828(5) Å in 4 indicates weak metal−metal interactions (see Figure S17, SI). 47,48 These interactions induce considerable change in the luminescence properties. 49 The Cu−P bond distance is 2.235(7) Å. 50 The Cu−I (μ 3 -I) bond distances vary from 2.695(4) to 2.752(4) Å and are marginally longer than the Cu−I (μ 2 -I) bond distances of 2.605(4) and 2.635(4) Å. 23 Complexes 2−4 have crystallographically imposed center of symmetry. ...
In this article the synthesis, structural studies and luminescence properties of CuI, AgI and AuI complexes of pyrimidine based phosphine C4H3N2-2-NH(CH2PPh2) (1) are described. The reactions of 1 with CuX, led to the isolation of 1-dimensional (1-D) chain, tetranuclear ladder or cyclic derivatives. The structural features of these complexes are greatly influenced by the metal-to-ligand ratio, reaction conditions and CuX (X = Cl, Br or I) employed. In the case of CuCl and CuBr, 1-dimensional coordination polymers [{CuCl}{C4H3N2-2-NH(CH2PPh2)}] (2) and [{CuBr}{C4H3N2-2-NH(CH2PPh2)}] (3) were obtained, whereas CuI afforded tetracopper complex [{CuI}4{C4H3N2-2-NH(CH2PPh2)}2(NCCH3)2] (4) having Cu4-ladder structure supported by P∩N bridging coordination of 1. The reaction of 1 with AgOTf yielded unprecedented 1-dimensional chain structure [{AgOTf}{C4H3N2-2-NH(CH2PPh2)}] (5), whereas the reaction with AgBF4 produced a 12-membered dinuclear complex, [{Ag}{C4H3N2-2-NH(CH2PPh2)}]2[BF4]2 (6), with each silver atom having a linear geometry. Gold complex [{AuCl}{C4H3N2-2-NH(CH2PPh2)}]2 (7) was synthesized by reacting 1 with [AuCl(SMe2)]. Compounds 2‒4 were also prepared using a pestle and mortar by grinding method in almost quantitative yield. Complex 4 with Cu∙∙∙Cu distance of 2.828(5) Å shows high luminescence due to the non-bonded metal∙∙∙metal interac-tions.
... 4- 16 Although some structure-property relationships have been formulated, [17][18][19] TADF in copper complexes is still difficult to predict a priori, let alone to design TADF materials, as it is an excited state property. In contrast, cuprophilic interactions can be prearranged in the ground state by careful choice of the ligand environment, and they have been shown to allow, albeit inefficiently, phosphorescence in simple dinuclear Cu I complexes with bridging diphosphines and other systems, [20][21][22][23] and also in clusters. [24][25][26] A few dicopper(I) complexes with short Cu-Cu contacts (o2.8 Å) have been reported to emit efficiently via TADF, but the influence of cuprophilic interactions in those has yet not been addressed. ...
This case study on a series of monomeric, dimeric and polymeric Cu(I) chlorido NHC-picolyl complexes shows that cuprophilic interactions can ensure strong spin-orbit coupling for fast (reverse)intersystem-crossing T1 ↔ S1 and T1 → S0, and therefore can serve as a design motif for the construction of highly efficient Cu(I)-based TADF or T1 emitters.
Applications of structurally well‐defined coinage‐metal nanoclusters (NCs) as optoelectronic materials and homogeneous catalysts have been restricted due to their inherent lower stability. Herein, the syntheses, structural characterizations, and photoluminescence properties of three novel air‐stable coinage‐metal(I) NCs‐supported by carbene‐anchored monoanionic phosphorus (cAAC=P⁻) with molecular formulae [(Cy‐cAACP)4(Cu)4(CuCl)4] (4), [(Cy‐cAACP)4(Ag)4(AgOTf)3] (5), and [(Cy‐cAACP)4(Ag)5]NTf2 (6) (cAAC = cyclic alkyl(amino) carbene; Tf = CF3SO2) exhibiting thermally activated delayed fluorescence (TADF) are reported. Apart from attractive metallophilic interactions [M─M; M ═ Cu, Ag], the enhanced kinetic and thermodynamic stability of 4–6 can be attributed to the excellent π‐accepting ability of cAAC=P⁻ surrounding the metallic cores. cAAC=P⁻ anion is generated either in situ by anion‐induced cleavage of P−Sb/B bonds of corresponding stibanyl/boryl phosphaalkenes in the presence of coinage‐metal(I)‐Cl/OTf/NTf2 salts or by directly introducing alkali‐metal phosphinidenide. The TADF properties of 4–6 are established by smaller energy gaps between the lowest singlet excited state and triplet excited state. In solid‐state, the delayed fluorescence lifetimes of 4–6 are found to be in the microsecond range with absolute photoluminescence quantum yields up to 20%. The redox‐active Cu(I)8 NC 4 is successfully exploited as an efficient photo‐catalyst for the selective carbene transfer reaction at ambient conditions, affording cyclopropanated indoles/styrenes with excellent yields and diastereoselectivity.
Metallophilic interactions are now a well-established phenomenon in chemistry. There are thousands of demonstrated examples from numerous different metals in homonuclear and heteronuclear combinations that are most commonly dinuclear but are also present in higher nuclearities as well. Definitive characterization originally came from SCXRD studies, which is now broadened with a wide array of solution and solid-state spectroscopic techniques, and increasingly sophisticated computational work. This Chapter gives an overview of metallophilic interactions through the literature of 2020. The examples are organized first by the participating metal centers and then by the structural motifs in which they are found. Complementary overviews of the synthetic and spectroscopic methods, as well as an introduction to the theoretical electronic structure framework, are also provided.
The review is a follow-up of a previous article (I. Haiduc, J. Coord. Chem. (2019). DOI: 10.1080/00958972.2019.1641702), which introduced structures with five-membered nitrogen heterocycles as inverse coordination centers. This review presents a panorama of organic six-membered nitrogen heterocycles acting as center cores in inverse coordination metal complexes and covers pyrazine, pyrimidine, pyridazine, triazine, tetrazine, pyridine, polypyridines, piperidine, diazabicyclooctane (DABCO) and urotropine (hexamethylenetetramine) playing such a role.
We prepared alkoxide-bridged heterometallic clusters of cerium and copper by the complexation of two metal alkoxides: treatment of Ce(O
t
Bu)4 with [Cu(O
t
Bu)]4 in a 1:1 metal ratio produced an alkoxide-bridged tetranuclear cluster, Ce2Cu2(O
t
Bu)10 (1). Upon adding 4-substituted pyridine derivatives to complex 1, trinuclear clusters, Ce2Cu(O
t
Bu)9(L) (2a: L = DMAP (4-dimethylaminopyridine); 2b: L = BPY (4,4'-bipyridine)), were obtained along with the release of 0.25 equiv of [Cu(O
t
Bu)]4, in which a three-coordinated copper center was involved. In contrast, reaction of 1 with 4 equiv of 2,6-dimethylphenylisocyanide (XylNC) and 0.5 equiv of [Cu(O
t
Bu)]4 resulted in the selective formation of CeCu2(O
t
Bu)6(CNXyl)2 (3). In addition, Ce2K(O
t
Bu)9 was used for complexation with CuCl2 by salt-elimination, giving Ce2CuCl(O
t
Bu)9 (4) including a five-coordinated copper center. These complexes 1-4 were characterized by crystal structure determination as well as cyclic voltammetry of 1, 2a, and 4. The cyclic voltammogram of 4 in CH2Cl2 and THF suggested that reorganization of the coordination sphere around the copper center was observed for 4 during the Cu(I/II) redox processes assisted by the coordination of THF.
A series of easily accessible linear N-heterocyclic carbene (NHC) copper(I) complexes, bearing pyridine (py) and its derivatives as chromophore ligands, are barely emissive in the single-crystalline solid state. However, their powders, neat films, and dilute doped films of poly(methyl methacrylate) (PMMA; 1-10%) show very intense blue-to-blue-green photoluminescence with remarkable quantum yields φ of up to 87% and microsecond lifetimes, indicative of triplet states being involved. These luminescence properties are similar to trigonal coordinated NHC copper(I) bis(pyridine) complexes, which we have also isolated and characterized with respect to their structures and photophysics. Our spectroscopic and theoretical studies provide detailed insight into the nature of the luminescence enhancing effect of the linear two-coordinated copper(I) compounds, which is based on the formation of Cu-F interactions between the BF 4⁻ anions and [Cu(NHC)(2-R-py)] ⁺ (R = H, Me, Ph) cations. These interactions are absent in the single crystals but lead to a distorted ground-state structure in the precipitated powders or in PMMA films, giving rise to high k r . In addition, we found that our linear copper(I) complexes exhibit mechanochromic luminescence because grinding of the single crystals leads to enhanced emission intensity. In light of the recently reported cation-anion contact-induced mechanochromic luminescence of two-coordinated copper(I) complexes, this study supports the generality of this new mechanism for the design of mechanoresponsive phosphorescent materials.
The copper compound [Cu(C 6 Cl 2 F 3 )(tht)] 4 (1) (tht: tetrahydrothiophene) is an excellent catalyst for the trans-to-cis isomerization of complexes [PdAr 2 (tht) 2 ](Ar: fluoroaryl) and also for the exchange of aryls between those palladium complexes. Herein, we also communicate the synthesis and characterization of 1 and some of its derivatives. The X-ray structure of 1 shows a linear chain of copper atoms, supported by fluoroaryl rings. The nuclear magnetic resonance ¹⁹ F diffusion-ordered spectroscopy study indicates that this structure is preserved in solution, although it is in equilibrium with other species.
A (2+2) dipodal condensation of bis{6‐formyl‐(2,3,4‐trimethoxy)phenyl}mercury (14) with various 1,2‐disubstitued diamines e.g., ethylenediamine, trans‐1,2‐diaminocyclohexane and o‐phenylenediamine led to the formation of 22‐membered mercuraazametallamacrocycles, [Hg‐{1‐C6H‐2,3,4‐(OCH3)3‐6‐(CHN)}2‐CH2‐CH2]2 (15), [Hg‐{1‐C6H‐2,3,4‐(OCH3)3‐6‐(CHN)}2‐C6H10]2 (16) and [Hg‐{1‐C6H‐2,3,4‐(OCH3)3‐6‐(CHN)}2‐C6H4]2 (17) respectively. The acceptor abilities and reactivities of the macrocycles are compared with the corresponding 22‐membered mercuraazametallamacrocycles obtained from the condensation of bis(formylphenyl)mercury (12) with the diamines. Also attempts have been made to prepare macrocyles with functionalized aryldiamies. Orange colored Cu(I) complexes, 24 ([15.Cu]ClO4) and 26 ([16.Cu]ClO4), were obtained upon the treatment of [Cu(CH3CN)4ClO4] with macrocycles 15 and 16, respectively. Similarly, brown colored Ag(I) complexes, 25 ([15.Ag]ClO4), and 27 ([16.Ag]ClO4) were isolated by reacting macrocycles 15 and 16 with AgClO4. The reaction of macrocycle 15 with equimolar Pt(COD)Cl2 afforded cyclometalated platinum(II) complex, Pt‐{1‐C6H‐2,3,4‐(OCH3)3‐6‐(CHN‐CH2}2 (28). Bis(2‐amino‐5‐methylphenyl)mercury (23), shows a very strong intermolecular Hg***Hg interaction. Density functional theory calculations and atoms in molecules analysis revealed the presence of metallophilic d10***d10 interactions as well as d10***d8 interactions in the synthesized compounds.
Synthesis and characterization of three hexa‐copper(I) extended metal atom chains (EMACs) and two dodecacopper(I) aggregates assembled by two hexadentate bis(pyridylamido)amidinate‐supported hexacopper(I) string complexes (monomers) via the ligand‐unsupported cuprophilicity are described. The hexa‐copper(I) EMACs show distinct coordination chemistry upon coordination of THF molecules. One is ligated by one THF molecule at the Cu3, while one is coordinated by two THF molecules at the Cu2 and Cu5. These Cu‐THF bonds are so weak that THF ligands readily dissociate upon dissolution in organic solvents to give dodecacopper(I) aggregates. In addition to short unsupported Cu‐Cu contacts, two hexacopper fragments in these two dodecacopper EMACs show a bent conformation based on X‐ray crystallography. Compared with their THF‐bound hexacopper(I) monomers and protonated ligands, these ligand‐unsupported cuprophilic interactions are shown to be weak by Raman spectroscopy. DFT calculations suggest the ligand‐unsupported cuprophilicity orginate from weak attractive orbital interactions, and the strength is estimated to be 2.4 kcal/mol.
Synthesis and characterization of three hexa‐copper(I) extended metal atom chains (EMACs) and two dodecacopper(I) aggregates assembled by two hexadentate bis(pyridylamido)amidinate‐supported hexacopper(I) string complexes (monomers) via the ligand‐unsupported cuprophilicity are described. The hexa‐copper(I) EMACs show distinct coordination chemistry upon coordination of THF molecules. One is ligated by one THF molecule at the Cu3, while one is coordinated by two THF molecules at the Cu2 and Cu5. These Cu‐THF bonds are so weak that THF ligands readily dissociate upon dissolution in organic solvents to give dodecacopper(I) aggregates. In addition to short unsupported Cu‐Cu contacts, two hexacopper fragments in these two dodecacopper EMACs show a bent conformation based on X‐ray crystallography. Compared with their THF‐bound hexacopper(I) monomers and protonated ligands, these ligand‐unsupported cuprophilic interactions are shown to be weak by Raman spectroscopy. DFT calculations suggest the ligand‐unsupported cuprophilicity orginate from weak attractive orbital interactions, and the strength is estimated to be 2.4 kcal/mol.
Coordination polymers (CPs) with bismuth(III) as connectivity centre have been prepared from BiX3 (X = Cl – I) and 4,4’-bipyridine (bipy) in order to implement Bi-based luminescence. The products were obtained via different synthetic routes like solution chemistry, melt syntheses or mechanochemical reactions. Five neutral and anionic 1D-CPs are presented that show a chemical parallel to trivalent lanthanides forming isostructural or closely related 1D-CPs, of which five additional compounds are described. Bi³⁺ proves a versatile cation for luminescence resulting from energy transfer processes between metal and ligand in the presented CPs. Quantum chemical calculations were carried out to investigate Bi³⁺ participation in the luminescence processes. The calculated results allow an assignment of the bright transitions composed of mainly metal-to-ligand-charge transfer (MLCT) character. These results show that Bi³⁺ can form strongly luminescent coordination compounds with N-donor ligands.
Salts of anionic silver(I) clusters with the carba-closo-dodecaboranylethynyl ligand were obtained from {Ag2(12-C≡C-closo-1-CB11H11)}n (1), selected pyridines, and [Et4N]Cl or [Ph4P]Br. Salts of octahedral silver(I) clusters [Et4N]2[Ag6(12-C≡C-closo-1-CB11H11)4(4-X-C5H5N)x] were formed with pyridine (x = 8, 5), 4-methylpyridine (x = 8, 6), and 4-cyanopyridine (x = 10, 7). In contrast, 3,5-lutidine (3,5-Me2Py) did not result in salts of dianionic clusters, even in the presence of an excess of [Et4N]Cl or [Ph4P]Br, but in salts of monoanionic AgI7 clusters, [Et4N][Ag7(12-C≡C-closo-1-CB11H11)4(3,5-Me2Py)9] (8) and [Ph4P][Ag7(12-C≡C-closo-1-CB11H11)4(3,5-Me2Py)13] (9). The AgI7 cluster in 8 is a pentagonal bipyramid whereas the one in 9 is an edge-capped octahedron. Compounds 6, 8, and 9 show green phosphorescence at room temperature. Although argentophilic interactions give rise to sufficient spin-orbit coupling for intersystem-crossing S1→Tn and moderate to high radiative rate constants, time-resolved measurements indicate that the quantum yields are greatly influenced by the pyridine ligands, which mainly determine the non-radiative rate constants. In addition, the crystal structures of [Ag16(12-C≡C-closo-1-CB11H11)8(Py)9.25(CH3CN)2(CH2Cl2)0.75]·CH2Cl2, [Ag8(12-C≡C-closo-1-CB11H11)4(Py)12], [Ag10(12-C≡C-closo-1-CB11H11)4(4-MePy)10Br2], [Ag7(12-C≡C-closo-1-CB11H11)3(4-tBuPy)11Cl]·(4-tBuPy), and [Ag9(12-C≡C-closo-1-CB11H11)4(3,5-Me2Py)11Cl] were elucidated.
Addition of 2 equiv. of CuI to a [Cu]4 multimetallic complex results in cluster formation leading to the isolation of a rare bicapped tetrahedral [Cu6I2] cluster that is stabilised by two conformationally constrained polynucleating ligands.
Among the coinage metal complexes displaying luminescent properties, those bearing C-donor aryl ligands have an increasing part in the chemistry of these metals. These types of ligands confer a high kinetic and thermodynamic stability on the complexes, but they can also be involved in the photoluminescent behaviour of the complexes. The development of new aryl-containing complexes of group eleven metals, the study of their photoluminescent properties and their related properties and applications are discussed in this perspective. Among these, luminescent gold(i) and gold(iii) compounds are being intensively used for the development of new properties with potential applications such as, for instance, electroluminescence, triboluminescence, mechanochromism, aggregated induced emissions, quenching, luminescent liquid crystals, low molecular weight gelators and photocatalysts, among others.
The photophysical properties of four, two-coordinate, linear diamidocarbene copper(i) complexes, [(DAC)2Cu][BF4] (1), (DAC)CuOSiPh3 (2), (DAC)CuC6F5 (3) and (DAC)Cu(2,4,6-Me3C6H2) (4) (DAC = 1,3-bis(2,4,6-trimethylphenyl)-5,5-dimethyl-4,6-diketopyrimidinyl-2-ylidene) have been investigated. Complex 1 shows a high photoluminescence quantum efficiency (ΦPL) in both the solid state (ΦPL = 0.85) and in CH2Cl2 solution (ΦPL = 0.65). The emission band of 1, both as a crystalline solid and in solution, is narrow (fwhm = 2300 cm(-1)) relative to the emission bands of 2 (fwhm = 2900 cm(-1)) and 3 (fwhm = 3700 cm(-1)). Complexes 2 and 3 are each brightly luminescent in the solid state (ΦPL = 0.62 and 0.18, respectively), but markedly less so in CH2Cl2 solution (ΦPL = 0.03 and <0.01, respectively). Complex 4 is not emissive in either the solid state or in solution. Phosphorescence of 1 in CH2Cl2 solution shows negligible quenching by oxygen in CH2Cl2 solution. This insensitivity to quenching is attributed to the excited state redox potential being insufficient for electron transfer to oxygen.
New tetranuclear supramolecular precursors [(R - C≡C - C≡C)Ag]4 (R = ⁱPr, tBu, and chx) are employed to construct a series of heterometallic silver(I)-copper(I) alkyl-1,3-diynyl cluster complexes (1-9) that bear a common CuAg3 core (normally trigonal-planar, but can be distorted to pyramidal) consolidated by cupro-argentophilic interaction under 3.12 Å, as found in 1 and 2. The photophysical properties of the multinuclear supramolecular precursors and selected complexes have been investigated. The present results strongly suggest that the assembly of medium-nuclearity clusters 3 to 9 is initiated by accretion of additional Ag(I) ions by the ubiquitous CuAg3 template through argentophilic (<3.4 Å) interaction, with cooperative cuprophilic enhancement (<2.76 Å) in the case of compound 9. To our knowledge, the present study provides the first report of conversion of a Group 11 homonuclear cluster into a heteronuclear one of higher nuclearity via inner-core expansion.
Primary arylamines are an important unit broadly found in synthetic, bio, and materials science. Herein we describe the development of a (NHC)Cu system that mediates a direct C-H amidation of (hetero)arenes by using N-chlorocarbamates or their sodio derivatives as the practical amino sources. A facile stoichiometric reaction of reactive copper-aryl intermediates with the amidating reagent led us to isolate key copper arylcarbamate species with the formation of a C-N bond. The use of t-BuONa base made this transformation catalytic under mild conditions. The present (NHC)Cu-catalyzed C-H amidation works efficiently and selectively on a large scale over a range of arenes including polyfluorobenzenes, azoles, and quinoline N-oxides. Deprotection of the newly installed carbamate groups such as Boc and Cbz was readily performed to afford the corresponding primary arylamines.
A potentially tridentate hemilabile ligand, PPh2-C6H4-PPh(O)-C6H4-PPh2 (P3O), has been used for the construction of a family of bimetallic complexes [MM'(P3O)2](2+) (M = M' = Cu (1), Ag (2), Au (3); M = Au, M' = Cu (4)) and their mononuclear halide congeners M(P3O)Hal (M = Cu (5-7), Ag (8-10)). Compounds 1-10 have been characterized in the solid state by single-crystal X-ray diffraction analysis to reveal a variable coordination mode of the phosphine-oxide group of the P3O ligand depending on the preferable number of coordination vacancies on the metal center. According to the theoretical studies, the interaction of the hard donor P[double bond, length as m-dash]O moiety with d(10) ions becomes less effective in the order Cu > Ag > Au. 1-10 exhibit room temperature luminescence in the solid state, and the intensity and energy of emission are mostly determined by the nature of metal atoms. The photophysical characteristics of the monometallic species were compared with those of the related compounds M(P3)Hal (11-16) with the non-oxidized ligand P3. It was found that in the case of the copper complexes 5-7 the P3O hybrid ligand introduces effective non-radiative pathways of the excited state relaxation leading to poor emission, while for the silver luminophores the P[double bond, length as m-dash]O group leads mainly to the modulation of luminescence wavelength.
In this work, two polymorphs and a pseudopolymorph of a trinuclear copper(I) pyrazolate complex, namely, [Cu(L-Br)]3 (L-Br = 4-(4-bromophenyl)-3,5-dimethylpyrazolyl), were isolated. One of them shows remarkable molecular shape curving, which is imposed by short intermolecular CuI-CuI interaction and parallelogram-like Br4 halogen bonding. These two sets of noncovalent interactions propagate along different directions and do not interact directly with each other. Interestingly, these cooperative interactions give rise to an undulating layer in the crystal structure of one polymorph. We used a variety of theoretical methods, such as electron density distribution (e.g., atoms-in-molecules analysis and reduced-density-gradient mapping), molecular orbitals, charge analysis, electrostatic potentials, and Hirshfeld surface analysis, to demonstrate the nature and strength of multiple CuI-CuI and Br···Br bonding qualitatively and quantitatively. Moreover, preliminary calculations based on time-dependent density functional theory were performed to shed light on the structure-property correlation of this luminescent complex.
Ausgehend von {Ag2(12-C≡C-closo-1-CB11H11)}n und ausgewählten Pyridinliganden wurden photostabile AgI-Cluster synthetisiert, die, mit einer Ausnahme, eine für AgI-Verbindungen ungewöhnliche Raumtemperaturphosphoreszenz zeigen. Eine besonders intensive Phosphoreszenz wurde für einen verzerrt pentagonal-bipyramidalen AgI7-Cluster mit einer für AgI-Cluster präzedenzlosen Quantenausbeute von Φ=0.76 beobachtet. Das Lumineszenzverhalten korreliert mit der Struktur des zentralen AgIn-Motivs, was anhand des Vergleichs der Emissionseigenschaften der Cluster mit unterschiedlicher Anzahl von AgI-Ionen, unterschiedlicher Ladung und elektronisch unterschiedlichen Pyridinliganden deutlich wird.
{Ag2 (12-C≡C-closo-1-CB11 H11 )}n and selected pyridine ligands have been used for the synthesis of photostable Ag(I) clusters that, with one exception, exhibit for Ag(I) compounds unusual room-temperature phosphorescence. Extraordinarily intense phosphorescence was observed for a distorted pentagonal bipyramidal Ag(I) 7 cluster that shows an unprecedented quantum yield of Φ=0.76 for Ag(I) clusters. The luminescence properties correlate with the structures of the central Ag(I) n motifs as shown by comparison of the emission properties of the clusters with different numbers of Ag(I) ions, different charges, and electronically different pyridine ligands.
A trio of dimeric copper(I) complexes of the formula [(Ph3P)Cu(μ-X)2Cu(PPh3)] (X = OC6F5, 1, OC4F9, 2, OCPh(CF3)2, 3) were prepared and characterized by X-ray crystallography, elemental analysis, and NMR spectroscopy (1H, 13C, 19F, 31P), as was the monomeric [(cy3P)Cu(OC4F9)] (cy = cyclohexyl, 4). Solution conductivity studies demonstrate that all three new dinuclear compounds, as well as the known [(Ph3P)Cu(μ-OC4H9)2Cu(PPh3)], 2-H, are neutral species in solution and do not rearrange into ion pairs. The fold angle (β) varies among these four dimers and the Cu(I)…Cu(I) distance in the structure of 2, 2.8315(5) Å, is cuprophilic. The Cu(I)…Cu(I) distances for 1, 2-H, and 3 are 3.0533(5), 2.890(2), and 3.0169(6) Å respectively. Density functional theory (DFT) calculations were performed on 1, 2, 3, and 2-H, as well as the hypothetical 1-H, and several related models. Five PMe3 models, 1(Me), 1-H(Me), 2(Me), 2-H(Me), and 3(Me) were also studied as well as five monomers [(Me3P)CuX] 1-mon, 1-H(mon), 2-mon, 2-H(mon), and 3-mon to understand the electronic reasons for folding in this group of compounds. A Natural Energy Decomposition Analysis (NEDA) indicates that electrostatic stabilizations are the dominant factor governing the strength of interaction between monomeric fragments in 1(Me) – 3(Me). NBO analysis reveals that 1(Me) and 1-H(Me) do not display any cuprophilic interactions. The folding angle observed in 2(Me), 2-H(Me), and 3(Me), which is correlated with an increased delocalization from the oxygen 2pz lone pairs, brings the metal centers into sufficient propinquity to have weak Cu…Cu orbital interactions. Weak luminescence behavior at room-temperature is also consistent with these assignments.
Although 2-phenylpyridine (ppy)-type complexes have been employed very successfully for the design of luminescent IrIII and PtII complexes, corresponding d10-coinage metal complexes are unknown. We report on the synthesis of the first, room-temperature-stable, CuI ppy-type complexes, by C-H activation of 2-(2,3,4,5-tetrafluorophenyl)pyridine (Htfppy, 1) using [Cu(OH)(IDipp)] (2) (IDipp = bis(2,6-di-isopropylphenyl)imidazole-2-ylidene) or by lithiation of 1 and subsequent reaction with CuBr·SMe2 in the presence of a POP ligand (POP = bis{2-(diphenylphosphanyl)phenyl} ether) in THF, giving [Cu(tfppy)(IDipp)] (3) or [Cu(tfppy)(POP)] (4). The complexes thus obtained adopt distorted trigonal and tetrahedral coordination geometries, respectively. Gold(I) tfppy complexes with IDipp (5) or PTol3 (6) ligands have also been prepared, showing a preference for linear coordination environments due to the noncoordinating pyridine moiety of the tfppy ligand. These structural differences have a profound effect on the photophysical properties of the coinage metal ppy compounds. The CuI tfppy complexes exhibit intense orange-red luminescence (λmax = 610 (3), 607 (4) nm) from a 3(intraligand)CT state in the solid state at room temperature, with phosphorescence lifetimes of τ = 8.6 (3) and 9.5 (4) μs. In contrast, the linear coordination leads to weak emission of the AuI complexes, with 5 displaying simultaneous fluorescence and phosphorescence. Surprisingly, reaction of 2 with Htfppy (1) in MeCN leads to solvent activation and to isolation of a copper acetamide complex, [Cu(N(H)C(O)Me)(IDipp)] (14).
By using environmentally friendly K-2[Ni(CN)(4)] that slowly hydrolyse upon hydrothermal treatment, cis-[Ni (CN)(2)(H2O)(4)] units and cyanides were generated and further assembled with Cu (I) atoms into pentagonal heterometallic ribbons. Subsequently, these pentagonal ribbons are induced aggregation via cuprophilic interactions into 2D supramolecular coloured polymorphs [(CuCN)(2)Ni (CN)(2)(H2O)(4)] (1 and 2). Dark blue 1 synthesized at a lower temperature is a denser phase while purple 2 synthesized at a higher temperature is a looser phase, which is abnormal to general rule that a higher reaction time and pressure tends to form a denser phase. Careful examination on structures reveals that slight size difference in pentagons and different interlayer distances of 2D supramolecular arrangement contribute to the abnormality. Besides, the titled compounds could be rare cuprophilicity drived examples of coloured polymorphs, which exhibit remarkable colour difference from dark-blue to purple. Magnetic measurements confirmed that diamagnetic MO atom in square planar [Ni(CN)(4)](2-) is transformed into octahedral coordinated Ni(I)with ground state spin S=1. CCDC: 1046750, 1; 1046751, 2.
Compounds containing copper(I) are of interest for their role in biological processes. The nature of short (< ∼3.2 Å) Cu⋯Cu contacts within these compounds has been debated, being either described as weakly attractive (bonding) ‘cuprophilic’ interactions, or simply as short metal–metal distances constrained by ligand geometry or largely ionic in nature. The title three-dimensional Cu⁺-containing coordination polymer, [Cu3(C7H7N2O2)Cl2]n, was formed from the in situ reduction of CuCl2 in the presence of 3,5-diaminobenzoic acid and KOH under hydrothermal conditions. Its complex crystal structure contains ten distinct CuI atoms, two of which lie on crystallographic inversion centres. The copper coordination geometries include near-linear CuOCl and CuN2, T-shaped CuOCl2 and distorted tetrahedral CuOCl3 groups. Each CuI atom is also associated with two adjacent metal atoms, with Cu⋯Cu distances varying from 2.7350 (14) to 3.2142 (13) Å; if all these are regarded as ‘cuprophilic’ interactions, then infinite [01] zigzag chains of CuI atoms occur in the crystal. The structure is consolidated by N—H⋯Cl hydrogen bonds.
In copper(I) chemistry, 'CuH in a bottle' is noteworthy, as is a rare example of CO and perchlorate in the same coordination sphere. Geochemists will be interested in the observation of oxygen exchange between sulfate and non-coordinated water in CuSO4·5H2O. In copper(ii) chemistry, the complex role of phosphate as a bridging ligand - including an example of μ3-η4-PO43- - is becoming apparent, and further examples of CuII-C(sp3) bonds have been identified.
This chapter presents selected complexes in which interactions among individual metal centers illustrate key concepts of bonding. It begins with formally noncovalent interactions, including the metallophilic interactions between M(I) centers as well as stronger three-center, two-electron interactions. Supported and unsupported complexes are discussed. Finally, heterometallic complexes displaying important reactivity are introduced.
1Introduction2Alkyl- and Arylcopper(I) Compounds3Organocopper(I) Copper(I)-X Aggregates (X = Monoanionic Group)4Cyclopentadienylcopper(I) Compounds5Copper Carborane Compounds6Copper(I) Acetylides7Organocuprates8Organocopper(II) and Organocopper(III) Compounds9Copper Carbene Complexes10Conclusions
Keywords:structural organocopper chemistry;alkyl- and arylcopper(I) compounds;highly explosive copper(I) acetylide Cu2C2;alkyl- and arylcopper(I) compounds;donor-acceptor complexes of organocopper compounds (RCu)-L;organocopper donor ligand adducts - distinctly monomeric species;organocopper(I) copper(I)-X aggregates (X = monoanionic group);cyclopentadienylcopper(I) compounds
Flexible host frameworks of mononuclear coordination complexes were designed and encapsulated for several organic guest molecules through electrostatic interactions in their crystals, in which the unique guest recognitions and the uniform cavities were induced by fluorination of the coordination complexes. These unusual pseudopolymorphic cocrystal states of the fully fluorinated coordination complex, bis[bis(2,3,4,5,6-pentafluorobenzoyl)methanido]copper(II) (1), achieved several guest encapsulations, e.g., three benzenes; four toluenes; one, two, and four p-xylenes; one and two m-xylenes; one o-xylene; two mesitylenes; one durene; one and two anisoles; and two dimethoxybenzenes. Based on X-ray crystallographic studies of these crystals, the axial positions on the metal and the surrounding spaces by the pentafluorophenyl groups produced the flexible cavity, and the guest molecules were recognized by the cooperative effects of metalπ and arene–perfluoroarene interactions. However, the guest recognition of partially fluorinated coordination complexes, in which the pentafluorophenyl groups of 1 were replaced by 2,3,5,6-tetrafluorophenyl (2), 2,4,6-trifluorophenyl (3a), 2,6-difluorophenyl (4a), and 4-fluorophenyl (5) groups, clearly depended on the fluorination numbers, e.g., the number of encapsulated benzene molecules was three (1) > two (2 and 3a) > zero (4a and 5). No encapsulation was observed with any guest molecules for 4a, although cavity spaces similar to 1, 2, and 3a were present around the axial position on the metal as the result of steric hindrance of the ortho-substituted fluorines. Thermal studies of the corresponding guest releases also indicated that the number of fluorinations amplified the host–guest interactions. The cocrystals exhibit reversible guest encapsulation and release processes with the same and different guest molecules, which can be clearly monitored by color change and thermogravimetric observations. We now report the synthesis of fully and partially fluorinated β-diketonato Cu2+ complexes and their unique guest encapsulation phenomena depending on the position and the number of fluorine substitutions using X-ray crystallography and thermal analysis. These results prove that simple mononuclear complexes become host materials due to fluorination effects.
Seven coinage metal(I) complexes bearing two different triazole-based N-heterocyclic carbene (NHC) ligands, [1-tert-butyl-4-{2-[(N,N-dimethylamino)methyl]phenyl}-3-phenyl-1H-1,2,4-triazol-4-ium-5-ide and 1-tert-butyl-4-(4-methylphenyl)-3-phenyl-1H-1,2,4-triazol-4-ium-5-ide] were synthesized and fully characterized in solution by NMR spectroscopy as well as in solid state by X-ray diffraction techniques. Furthermore, the XRD analysis showed that the bidentate coordination of the amino group substituted NHC ligand, previously observed for rhodium and palladium complexes, does not take place in the solid state structure of Au(I) complexes with various halide ligands. Nevertheless, the formation of sets of two head-to-tail oriented monomers aggregated via a weak metallophilic contact was revealed for both NHC ligands as well as for all three coinage metals with different halides. These experimental data correlate quite well with the previously published theoretical study on related complexes.
The title compound, [Cu2(SCN)2(C13H14N2)]n, is a two-dimensional coordination polymer containing tetrahedrally coordinated CuI atoms bound to one N atom from a 1,3-di-4-pyridylpropane molecule, and one N and two S atoms from three distinct μ3-thiocyanate anions. The resulting [Cu2(SCN)2] staircase motifs align parallel to the b crystal axis and link through tethering 1,3-di-4-pyridylpropane ligands into layers parallel to the bc crystal plane. Distinct layers with subtly different conformations stack in a BAA′B′ pattern, where the BA and A′B′ double slabs are related by an inversion center.
To investigate the influence of the non-covalent interactions, such as hydrogen-bonding, π–π packing and d10–d10 interactions in the supramolecular motifs, three cyanido-bridged heterobimetallic discrete complexes {Mn(bipy)2(H2O)[Ag(CN)2]}[Ag(CN)2] (1), {Mn(phen)2(H2O)[Au(CN)2]}2[Au(CN)2]2·4H2O (2), and {Cd(bipy)2(H2O)[Au(CN)2]}[Au(CN)2] (3) (bipy = 2,2′-bipyridine, and phen = 1,10-phenanthroline), which are based on dicyanidometallate(I) groups with 1:2 stoichiometry of metal ions and 2,2′-bipyridyl-like co-ligands were synthesized and structurally characterized. In compound 1, hydrogen bonding and π–π interactions governed the supramolecular contacts. In compound 2, the incorporation of aurophilic, hydrogen bonding and π–π interactions result in a 3D supramolecular network. In compound 3, hydrogen bonding and π–π stacking interactions result in a 2D supramolecular layer. In the three complexes, hydrogen-bonding, π–π packing and/or d10–d10 interactions can play important roles in increasing the dimensionality of supramolecular assemblies.
Dieser Aufsatz beschreibt Phänomene der molekularen Erkennung von aromatischen Ringen in chemischen und biologischen Systemen in einem multidimensionalen Ansatz. Neue Ergebnisse aus der Wirt-Gast-Chemie, biologischen Affinitätsassays und Biostrukturanalysen, Datenbanksuchen in der Cambridge Structural Database (CSD) und der Protein Data Bank (PDB) und hochentwickelten Rechnungen, die seit dem Erscheinen eines früheren Aufsatzes in 2003 veröffentlicht wurden, sind hier zusammengefasst. Die Themen Aren-Aren-, Perfluoraren-Aren-, Schwefel-Aren-, Kation-π- und Anion-π-Wechselwirkungen sowie Wasserstoffbrücken zu aromatischen Systemen werden behandelt. Das gewonnene Wissen kommt besonders der strukturbasierten Hit-zur-Leitstruktur-Entwicklung und der Leitstrukturoptimierung sowohl in der pharmazeutischen als auch in der Pflanzenschutzindustrie zugute. Zudem erleichtert es die Entwicklung neuer Materialien und supramolekularer Systeme und soll zu weiteren Anwendungen von Wechselwirkungen mit aromatischen Ringen zur Kontrolle des stereochemischen Verlaufs chemischer Umsetzungen inspirieren.
A series of novel cyclic and V-shaped cuprous clusters, (HNEt3)2 [Cu6(bmsapy)4] (1), [Cu8(banlny)4] (2) and [Cu6(ansny)4Cl] (CF3SO3) (3), were synthesized. Compounds (1) and (2) possess a similar cyclic metal structural arrangement, and the metallic arrangement of compound (2) is as in (1) with an insertion of a pair of ligand-unbridged Cu(I) atoms. Compounds (1) and (2) both have unusual ligand-unbridged Cu(I)-Cu(I) separations, but compound (3) does not. The ligand-unbridged Cu(I)-Cu(I) distances in (2) are shorter than those in (1). In absorption spectra, compound (2) displayed red shifts from (1) due to the increase in nuclearity and the number of the aromatic rings in ligands. TDDFT calculations suggest that in HOMOs, the major molecular orbital contribution is from the six Cu(I) atoms implying that the photoluminescent property of (1) is dependent on the cyclic hexacopper arrangement rather than that of (HNEt3) [Cu3(btsapy)2] (4).
Since its first report in 1981, mesitylcopper has become an extremely popular and useful reagent, with many new applications emerging during the past decade. This review summarizes its structural and spectroscopic properties and gives a brief overview of the multitude of fascinating compounds and reactions that have been discovered by using mesitylcopper. Specifically, the role of mesitylcopper in synthesizing oligonuclear homo- and heteroleptic copper(I) frameworks, including biorelevant copper(I) complexes, and the application of mesitylcopper in stoichiometric and catalytic C–C and C–heteroatom bond-forming reactions and as a precursor for nanoparticles and intermetallic phases are covered.
The effect of the binding of pyridine ligands to pentafluorophenyl copper, [C6F5Cu]4 (1), on structural features and photophysical properties has been investigated through a combined multinuclear NMR, X-ray crystallography, and photoluminescence study. Reaction of 1 with 2 equiv of pyridine yields a novel pyridine complex, 3, in which the tetranuclear framework of 1 is retained. Complex 3 features a rhombus-shaped tetracopper core with a short diagonal Cu···Cu distance of 2.5941(6) Å between the dicoordinate copper centers and a longer distance between the pyridine-coordinated copper centers of 4.178(1) Å. In contrast, treatment of 1 with 4 equiv of pyridine results in complete breakdown of the tetranuclear aggregate to give the formally dicoordinate species C6F5Cu(py) (4-H). Reaction of 1 with 2,2′-bipyridine results in formation of the tricoordinate complex C6F5Cu(2,2′-bipy) (5). Aggregate breakdown in species 4 and 5 is reflected in a significantly reduced chemical shift difference Δδ(19Fmeta/para) and a strong downfield shift of the copper-bound carbon atoms in the 13C NMR spectra in comparison to 3. A dynamic equilibrium is established at ratios of py/C6F5Cu ranging from 0 to 2. The solid-state structures of all compounds have been determined by single-crystal X-ray crystallography. The supramolecular assembly of complex 3 via arene–arene π-interactions leads to a network structure with solvent-filled channels propagating through the lattice along the crystallographic c axis. The 2,2′-bipyridine complex 5 also shows π-stacking as the dominant feature in the extended solid-state structure. In contrast, a different mode of supramolecular assembly is found for 4-H in that cuprophilic interactions lead to assembly into one-dimensional copper chains with equidistant Cu···Cu contacts of 2.8924(3) Å. However, the closely related complexes 4-R with methyl or chloro substituents in either the ortho or the para position form supramolecular stacks with structural features that, again, are dominated by offset perfluoroarene–arene interactions with intermolecular plane-to-plane separations of ca. 3.3–3.6 Å. The dicoordinate copper atoms are aligned in one-dimensional chains with alternating short and long Cu(I)···Cu(I) distances of 3.531(1)/3.698(1) Å in 4-pMe, 3.2454(5)/4.2970(5) Å in 4-oMe, 3.521(1)/3.784(1) Å in 4-pCl, and 3.4797(6)/3.8363(6) Å in 4-oCl. Compound 4-H is strongly blue fluorescent at 460 nm in the solid state, but yellow-green fluorescent at 77 K, resulting in an interesting example of luminescence thermochromism. In contrast, the substituted compounds 4-R display strong luminescence only at liquid nitrogen temperature. In all cases, the fluorescence emission band is in the range of ca. 410–425 nm and thus at significantly different energy from that in 4-H, which strongly suggests that the short Cu···Cu contacts in 4-H give rise to unique luminescence properties.
A new primary explosive, the silver salt of 4,6-diazido-N-nitro-1,3,5-triazine-2-amine (AgDANT), was synthesized and characterized. AgDANT was prepared with a 97 % yield and characterized by IR spectroscopy, single-crystal X-ray diffraction, and DTA. The crystal density of AgDANT is 2.530 g cm−3 and the molecule consists of a centro-symmetric dimer with a high degree of planarity. The intramolecular AgAg distance is relatively low (331 pm) and can be considered as a strong argentophilic interaction. AgDANT is non-hygroscopic and its solubility in water (1.27 mg in 100 mL at 23 °C) is on a similar level of solubility to that of silver azide. The sensitivity of AgDANT to impact is slightly higher than that for MF, sensitivity to friction is the same as for LA, and sensitivity to electric discharge is between that for LS and MF. Initiation efficiency of AgDANT was tested in electric detonators and compared to dextrinated lead azide (initiation efficiency of AgDANT is 40 mg for PETN secondary charge). The thermal resistance of detonators with AgDANT is satisfactory; all detonators were fully functional after exposure at 65 °C (30 d) and 85 °C (2 d).
Homobimetallic metallophilic interactions between copper, silver, and gold-based [(NHC)MX]-type complexes (NHC=N-heterocyclic carbene, i.e, 1,3,4-trimethyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene; X=F, Cl, Br, I) were investigated by means of ab initio interaction energies, Ziegler-Rauk-type energy-decomposition analysis, the natural orbital for chemical valence (NOCV) framework, and the noncovalent interaction (NCI) index. It was found that the dimers of these complexes predominantly adopt a head-to-tail arrangement with typical M⋅⋅⋅M distance of 3.04-3.64 Å, in good agreement with the experimental X-ray structure determined for [{(NHC)AuCl}2 ], which has an Au⋅⋅⋅Au distance of 3.33 Å. The interaction energies between silver- and gold-based monomers are calculated to be about -25 kcal mol(-1) , whereas that for the Cu congener is significantly lower (-19.7 kcal mol(-1) ). With the inclusion of thermal and solvent contributions, both of which are destabilizing, by about 15 and 8 kcal mol(-1) , respectively, an equilibrium process is predicted for the formation of dimer complexes. Energy-decomposition analysis revealed a dominant electrostatic contribution to the interaction energy, besides significantly stabilizing dispersion and orbital interactions. This electrostatic contribution is rationalized by NHC(δ(+) )⋅⋅⋅halogen(δ(-) ) interactions between monomers, as demonstrated by electrostatic potentials and derived charges. The dominant NOCV orbital indicates weakening of the π backdonation in the monomers on dimer formation, whereas the second most dominant NOCV represents an electron-density deformation according to the formation of a very weak M⋅⋅⋅M bond. One of the characteristic signals found in the reduced density gradient versus electron density diagram corresponds to the noncovalent interactions between the metal centers of the monomers in the NCI plots, which is the manifestation of metallophilic interaction.
The preparation of a series of imidazolium salts bearing N-allyl substituents, and a range of substituents on the second nitrogen atom that have varying electronic and steric properties, is reported. The ligands have been coordinated to a copper(I) centre and the resulting copper(I)-NHC (NHC=N-heterocyclic carbene) complexes have been thoroughly examined, both in solution and in the solid-state. The solid-state structures are highly diverse and exhibit a range of unusual geometries and cuprophilic interactions. The first structurally characterised copper(I)-NHC complex containing a copper(I)-alkene interaction is reported. An N-pyridyl substituent, which forms a dative bond with the copper(I) centre, stabilises an interaction between the metal centre and the allyl substituent of a neighbouring ligand, to form a 1D coordination polymer. The stabilisation is attributed to the pyridyl substituent increasing the electron density at the copper(I) centre, and thus enhancing the metal(d)-to-alkene(π*) back-bonding. In addition, components other than charge transfer appear to have a role in copper(I)-alkene stabilisation because further increases in the Lewis basicity of the ligand disfavours copper(I)-alkene binding.
Reactions of (phenylethynyl)germylene LGeC≡CPh (L = HC[C(Me)N-2,6-iPr2C6H3]2) with 0.25 equiv of (CuC6F5)4, 1 equiv of AgC6F5·MeCN, and 1 equiv of AuC6F5·SC4H8, respectively, yielded LGe(C≡CPh)CuC6F5 (1), [(LGeC≡CPh)2Ag]+[Ag(C6F5)2]? (2), and LGe(C≡CPh)AuC6F5 (3). Complexes 1?3 were characterized by IR and NMR spectroscopy and X-ray crystallography. Compound 1 shows a bonding pattern of the CuC6F5 entity by both the phenylethynyl C≡C linkage and the L ligand backbone of the ?-C atom, while 3 exhibits a bonding mode of the AuC6F5 entity at the germylene center. Compound 2 is an ionic derivative featuring the Ge?Ag donor?acceptor bond formed under redistribution of the AgC6F5 entity. Further reactions of 1 with (CuC6F5)4, AgC6F5·MeCN, and AuC6F5·SC4H8 afforded the complexes LGe(C≡CPh)(CuC6F5)(MC6F5) (M = Cu (4), Ag (5), Au (6)). Compounds 4?6 were characterized by IR and NMR spectroscopy, and 5 and 6 were further investigated by X-ray crystallography. Compounds 4?6 all show an additional bonding of the respective MC6F5 moiety at the germylene center of 1. These studies reveal a multiple donor reactivity of LGeC≡CPh. The slightly different Lewis acidic properties of the congeneric pentafluorophenylcopper(I), -silver(I), and -gold(I) complexes as acceptors are thus disclosed.
A bent dicopper-hydride cation that has an N-heterocyclic carbene supporting ligand has a Cu-H-Cu angle of 122° in the solid state. Density functional theory suggests an open three-centered metal-hydrogen interaction. The hydride reacts readily with methanol and with carbon dioxide; insertion of phenylacetylene affords a gem-dicopper vinyl complex.
A phenyl and a 2,3,5,6-tetrafluorophenyl ring, each bearing a tris(n-dodecyloxy)benzylamine moiety via an amide bond, were tethered together through an imine linkage to give a non-covalent synthon (imine 1) with a strong capacity of supramolecular self-assembly. Gelation was observed in several organic solutions, within which fibrous aggregate morphologies were visualized by SEM and AFM. Both arene–perfluoroarene stacking and amide–amide hydrogen bonding interactions were responsible for such self-assembly behaviours, as evidenced by 1H NMR studies. Hydrolysis of the imine linkage catalyzed by acid strongly weakened the intermolecular interactions, resulting in dissociation of the low molecular weight gelator and giving rise to an acid-mediated gel–sol transition.
We have designed a supramolecular system to pre-organize the azide and alkyne functional groups via electrostatic and arene–perfluoroarene interactions. After pre-organization, high pressure was applied to accelerate the copper-free cycloaddition of the azide and alkyne groups in the crystalline state.
The homoleptic aryl copper reagent [Cu4Dipp4] (Dipp=2,6-diisopropylphenyl) has been prepared and structurally characterized by a single-crystal X-ray diffraction study. Its tetrameric structure differs in significant details from that of the previously reported [Cu4Tripp4] (Tripp=2,4,6-triisopropylphenyl). The electronic structure of the cluster has been probed through B3LYP/6311G(2d,p)//B3LYP/6-31G calculations on [Cu4Ph4] constrained to D2d symmetry. The utility of the new copper reagent is demonstrated by the preparation of pure DippPCl2, for which the crystal structure is also reported.
A chiral 2-naphthylferrocenylcopper heteroaggregate (2) was prepared in high yield by reaction of (Sp-2-naphthylferrocenyl)trimethyltin with (C6F5Cu)4 and fully characterized by multinuclear NMR, single crystal X-ray diffraction, and elemental analysis. The reactivity of 2 toward boron halides was examined. Rearrangement reactions resulted in formation of 1,2-, 1,3-, and 1,1′-disubstituted naphthylferrocenylboranes.
Terpyridine (terpy) (2) reacts with a 1:1 mixture of [{[Ti](μ−σ, π-CCSiMe3)2}Cu(NCMe)]PF6 (1) and [{[Ti](μ−σ,π-CCSiMe3)2}CuO2NO (4) ([Ti](η5-C5H4SiMe3)2Ti) to produce the polymeric copper strain {[Cu2(terpy)2]PF6, NO3}n (6) in which dimeric [Cu2(terpy)2]2+ units are linked by copper–copper interactions; a possible reaction mechanism is presented.
Organocopper reagents provide the most general synthetic tools in organic chemistry for nucleophilic delivery of hard carbanions to electrophilic carbon centers. A number of structural and mechanistic studies have been reported and have led to a wide variety of mechanistic proposals, some of which might even be contradictory to others. With the recent advent of physical and theoretical methodologies, the accumulated knowledge on organocopper chemistry is being put together into a few major mechanistic principles. This review will summarize first the general structural features of organocopper compounds and the previous mechanistic arguments, and then describe the most recent mechanistic pictures obtained through high-level quantum mechanical calculations for three typical organocuprate reactions, carbocupration, conjugate addition, and SN2 alkylation. The unified view on the nucleophilic reactivities of metal organocuprate clusters thus obtained has indicated that organocuprate chemistry represents an intricate example of molecular recognition and supramolecular chemistry, which chemists have long exploited without knowing it. Reasoning about the uniqueness of the copper atom among neighboring metal elements in the periodic table will be presented.
Gold(I) complexes of overall formula LAuCl (L = various methylpyridines) are non-conducting in acetone. X-ray structure analyses show that the solid state structure of the corresponding complex 1 (L = 2-picoline) is molecular; the 3-picoline derivative 2 is however ionic (L2Au)+(AuCl2)-. 3-Picoline forms a molecular complex LAuC6F5 (3) and also the ionic (L2Au)+(SbF6)- (4). Complexes 1, 2 and 4 display short Au⋯Au contacts, leading to chains of gold atoms; additionally, complexes 3 and 4 show weak Au⋯F contacts. The (3-picoline)-gold(III) complex trans-(L2AuCl2)+(SbF6)- (5) was obtained as a by-product; it too contains short Au⋯F contacts.
The synthesis of heterobimetallic {[Ti](C≡CR1)2}MX {[Ti] = (η5-C5H4SiMe3)2Ti; M = Cu, R1 = SiMe3: 4a, X = SCF3; 4b, X = SEt; M = Ag, R1 = tBu: 5a, X = OC(O)Me; 5e, X = NO3; M = Ag, R1 = SiMe3: 5b, X = OC(O)Me; 5c, X = OC(O)Ph; 5d, X = NO3} is described. These compounds together with {[Ti](C≡CR1)2}CuX (4c, R1 = SiMe3, X = SC6H4CH2NMe2-2; 4d, R1 = tBu, X = SC6H4CH2NMe2-2) can be used for the preparation of a large variety of different organo-copper(I) and -silver(I) species. The titanium-copper complexes {[Ti](C≡ CR1)2}CuR2 [R1 = SiMe3: 6a, R2 = C6F5; 6b, R2 = C6H2(CF3)3-2,4,6; 6c, R2 = C6H2Ph3-2,4,6; R1 = tBu: 6d, R2 = C6H2Ph3-2,4,6; 7, R2 = Me] are accessible by the reaction of 4c or 4d with suitable organic nucleophiles. Monomeric organo-silver(I) compounds can be prepared by using different starting materials: While the silver(I) aryls {[Ti](C≡CSiMe3)2}AgR2 [8a, R2 = C6H2(CF3)3-2,4,6; 8b, R2 = C6H2Ph3-2,4,6] are only available by the reaction of 5b with LiC6H2(CF3)3-2,4,6 or BrMgC6H2Ph3-2,4,6, the silver(I) methyl species {[Ti](C≡CR1)2}AgMe (9a, R1 = SiMe3; 9b, R1 = tBu) can be synthesized by using 5a, 5b, 5d, or 5e as starting materials. While compounds 6-8 are stable under the reaction conditions applied, 9a already starts to decompose at low temperature: The heterobimetallic titanium-silver acetylide {[Ti](C≡CSiMe3)(C≡CAg)}2 (10) is formed by nucleophilic substitution of one of the alkynyl Me3Si groups, whereby SiMe4 is eliminated. Moreover, compounds 6-9 react with Br2 to produce R2-Br along with {[Ti](C≡CR1)2}MBr (M = Cu; 11a, R1 = tBu; 11b, R1 = SiMe3; M = Ag, 11c, R1 = SiMe3), which yield with equimolar amounts of LiR2 or BrMgR2 the starting materials 6-9 back.The solid-state structures of 4a, 5c, 6c, and 8b are reported. All complexes contain a monomeric (η2-alkyne)2M(η1-X) (4,5) or (η2-alkyne)2M(η1-R2) (6-9) entity in which the group 11 metal atom M is trigonally coordinated by the two alkynyl ligands C≡CR1 and the η1-bonded groups X or R2, respectively.
Gold(I) complexes of overall formula LAuCl (L = various methylpyridines) are non-conducting in acetone. X-ray structure analyses show that the solid state structure of the cor responding complex 1 (L = 2-picoline) is molecular; the 3-picoline derivative 2 is however ionic (L2Au)+(AuCl2)-. 3-Picoline forms a molecular complex LAuC6F5 (3) and also the ionic (L2Au)+(SbF6)- (4). Complexes 1, 2 and 4 display short Au ··· Au contacts, leading to chains of gold atoms; additionally, complexes 3 and 4 show weak Au ··· F contacts. The (3-picoline)-gold(III) complex trans-(L2AuCl2)+(SbF6)- (5) was obtained as a by-product; it too contains short Au ··· F contacts.
A series of copper alkyls (methyl, ethyl and n-propyl) with ligands (2,2′-bipyridyl and tricyclohexylphosphine) and copper methyl without ligands has been prepared by the reaction of copper(II) acetylacetonate with dialkylaluminum monoethoxides in the presence or absence of the ligand in diethyl ether under nitrogen at low temperature. The copper alkyls were characterized by elemental analysis, chemical reactions, and by IR and NMR spectra. The ligand-free methylcopper is thermally very unstable and decomposed explosively; the bipyridyl ligand showed little effect on the stability of the copper alkyl. In contrast, the tricyclohexylphosphine-coordinated complexes are thermally very stable. Various reactions of the tricyclohexylphosphine-coordinated copper alkyls toward carbon dioxide, alkyl halides and olefins have been studied.
A number of polynuclear d10 transition metal complexes have been found to exhibit interesting luminescence properties. The photoluminescence properties of polynuclear d10 metal complexes are highly diversified. In the presence of a wide range of bridging and ancillary ligands, the excited states of such complexes have been suggested to range from metal-to-ligand charge-transfer, ligand-to-metal charge-transfer, metal-centred to ligand-centred in nature. Recent work on the photophysical and photochemical properties, as well as the applications of this class of luminescent polynuclear d10 metal complexes will be described in this review article.
Reactions of 2-bis (trimethylsilyl) methylpyridine, (1), with LiBun in hexane–diethyl ether, and LiBun in tetrahydrofuran followed by CuCl, yields thermally robust binuclear complexes [{2-(Me3Si)C2(M)C5H4N}2] for M = Li and M = Cu respectively in which the metal is not involved in electron deficient bonding, being bound by Cα of one ligand and the nitrogen of a centrosymmetrically related ligand and has a close metal contact [M M 2.560(9)(Li) and 2.412(1)Å(Cu)].
Dimeric [Cu2(PPh2Me)4(µ,η1-CCPh)2] has been synthesized and crystallographically characterized; its photophysics together with those of other related organocopper(I) complexes, [Cu2{2-C(SiMe3)2C5H4N}2] and [{Cu(C6H2Me3-2,4,6)}5] have been studied and Stern–Volmer quenching data of the phosphorescent state of the pyridine complex with organic halides are suggestive of a charge-transfer mechanism with a high driving-force regime.
Some complexes of organocopper(I) compounds with 2,2′-bipyridine, 4,4′- bipyridine, 1,10-phenanthroline, 1,2-bis(diphenylphosphino)ethane and bis(diphenyl- phosphino) methane have been isolated and characterized. The organocopper(I) complexes of 1,2-bis(diphenylphosphino)ethane reacted with dichloroethane to give vinylchloride and the corresponding copper halide complexes. Some new copper(I) chloride complexes of 1,2-bis(diphenylphosphino)ethane are also reported.
The reaction of 1,1'-bis(2-pyridyl)octamethylferrocene (L) with [Cu(NCMe)(4)]BF4 in CH2Cl2 affords [CuL][CuCl2], the structure of which is determined by a single-crystal X-ray diffraction study; this reveals a remarkably short ligand-unsupported Cu-I-Cu-I contact of 281.0(2) pm.
Molecular weight measurements and microwave titrations indicate that no interaction occurs between tetrameric 2-Me{2}NCH{2}C{6}H{4}Cu (Ar{4}Cu{4}) and the monodentate ligands PPh{3}, CH{3}CN or pyridine. However, the tetrameric structure Ar{4}Cu{4} breaks down upon interaction (1/1 molar ratio ArCu/L) with the bidentate ligands (L) Diphos or cis-DPPEE to give the monomeric 1/1 complexes ArCu . L.Addition of Diphos to ArCu . Diphos or conducting the reaction of Ar{4}Cu{4} with Diphos in a 1/2 ratio (ArCu/Diphos) gives rise to a C{a}{l}{k}@?P bond cleavage reaction resulting in the formation of dimeric (Ph{2}PCu . Diphos){2} . 2 C{6}H{6}, ArH and Ph{2}PCH@?CH{2}.The molecular structure of (Ph{2}PCu . Diphos){2} . 2 C{6}H{6}, has been determined by a single-crystal X-ray diffraction study. Crystals are monoclinic, space group P2{1}/c and have Z @? 2 in a unit cell of dimensions a @? 12.997(6), b @? 12.669(7), c @? 22.839(9) @9 and @b @? 94.48(4)}o{. The structure was refined to R @? 0.048 for 3048 independent reflections. The four copper atoms in the dimer are held together by two Ph{2}P bridges. The bonding in the dimer is discussed.
The synthesis of heterobimetallic {[Ti](CCR1)2}MX {[Ti] = (η5-C5H4SiMe3)2Ti; M = Cu, R1 = SiMe3: 4a, X = SCF3; 4b, X = SEt; M = Ag, R1 = tBu: 5a, X = OC(O)Me; 5e, X = NO3; M = Ag, R1 = SiMe3: 5b, X = OC(O)Me; 5c, X = OC(O)Ph; 5d, X = NO3} is described. These compounds together with {[Ti](CCR1)2}CuX (4c, R1 = SiMe3, X = SC6H4CH2NMe2-2; 4d, R1 = tBu, X = SC6H4CH2NMe2-2) can be used for the preparation of a large variety of different organo−copper(I) and −silver(I) species. The titanium−copper complexes {[Ti](CCR1)2}CuR2 [R1 = SiMe3: 6a, R2 = C6F5; 6b, R2 = C6H2(CF3)3-2,4,6; 6c, R2 = C6H2Ph3-2,4,6; R1 = tBu: 6d, R2 = C6H2Ph3-2,4,6; 7, R2 = Me] are accessible by the reaction of 4c or 4d with suitable organic nucleophiles. Monomeric organo−silver(I) compounds can be prepared by using different starting materials: While the silver(I) aryls {[Ti](CCSiMe3)2}AgR2 [8a, R2 = C6H2(CF3)3-2,4,6; 8b, R2 = C6H2Ph3-2,4,6] are only available by the reaction of 5b with LiC6H2(CF3)3-2,4,6 or BrMgC6H2Ph3-2,4,6, the silver(I) methyl species {[Ti](CCR1)2}AgMe (9a, R1 = SiMe3; 9b, R1 = tBu) can be synthesized by using 5a, 5b, 5d, or 5e as starting materials. While compounds 6−8 are stable under the reaction conditions applied, 9a already starts to decompose at low temperature: The heterobimetallic titanium−silver acetylide {[Ti](CCSiMe3)(CCAg)}2 (10) is formed by nucleophilic substitution of one of the alkynyl Me3Si groups, whereby SiMe4 is eliminated. Moreover, compounds 6−9 react with Br2 to produce R2−Br along with {[Ti](CCR1)2}MBr (M = Cu; 11a, R1 = tBu; 11b, R1 = SiMe3; M = Ag, 11c, R1 = SiMe3), which yield with equimolar amounts of LiR2 or BrMgR2 the starting materials 6−9 back.The solid-state structures of 4a, 5c, 6c, and 8b are reported. All complexes contain a monomeric (η2-alkyne)2M(η1-X) (4, 5) or (η2-alkyne)2M(η1-R2) (6−9) entity in which the group 11 metal atom M is trigonally coordinated by the two alkynyl ligands CCR1 and the η1-bonded groups X or R2, respectively.
The thermally stable tris(pyridyl) Al(III) complex [MeAl(2-py)3Li·THF] (1·THF), obtained from the reaction of lithiopyridine [2-pyLi] with MeAlCl2 (3:1 molar equiv, respectively), functions as a pyridyl-transfer reagent, as exemplified by the reaction of 1·THF with CuCl (1:1 molar equiv), which gives the Cu(I) organometallic [{Cu(2-py)}3]∞ (2). The solid-state structures of 1, the dimer [MeAl(2-py)3Li]2 ([1]2), and 2 are reported. Complex 2, which cannot be obtained by direct reaction of [2-pyLi] with CuCl, has a polymeric structure in which macrocyclic [Cu(2-py)]3 ring units form infinite offset stacks associated by short Cu···Cu interactions between three- and four-coordinate Cu(I) centers (2.762(3) Å).
The binding behavior of arenes toward pentafluorophenylcopper was investigated. Crystallization of pentafluorophenylcopper from a mixture of 1,2-dichloroethane and cyclohexane affords the homoleptic tetrameric complex [Cu(C6F5)]4, whereas a π-complex, [Cu(C6F5)]4(η2-toluene)2, is obtained from toluene solution. The unique coordination of two toluene molecules in [Cu(C6F5)]4(η2-toluene)2 leads to major structural changes as the regular square planar tetramer is distorted toward a butterfly structure with one short and one long diagonal Cu···Cu distance of 2.5935(3) and 3.955(1) Å, respectively. The toluene molecules are bound in an unsymmetrical η2-coordination mode with the shortest contacts observed between copper and the meta carbon atoms (d(Cu−C) = 2.271(2), 2.298(2) Å) and slightly longer distances to the para positions (d(Cu−C) = 2.339(2), 2.455(4) Å). Multinuclear NMR studies show that complexation to the intact tetrameric cluster species also occurs in neat solution of the aromatic species. Strongly coordinating solvents such as acetonitrile or DMSO, however, lead to aggregate breakdown.
The synthesis of homoleptic aryl derivatives of group 11 metals has been performed by reacting the monochlorides [CuCl], [AgCl], and [AuCOCl] with MesMgBr (Mes ≡ 2,4,6-Me3C6H2). The resulting products [Cu5Mes5] (1), [Ag4Mes4] (2), and [Au5Mes5]·2THF (3) have been isolated as crystalline thermally stable compounds. They have, in the solid state, cyclic structures whose molecular geometries are discussed within. MW determination by cryoscopy in benzene and 1H NMR spectra in both C6D6 and C6D12 showed that the three oligomeric structures were in equilibrium with the respective dimeric form of the molecule. In each case the dimeric form was the prevailing species in solution. The solution equilibrium was very rapidly established for the silver and gold complexes and was relatively slower for the copper complex. In the case of the copper complex the rate of equilibrium was solvent dependent, being much faster in toluene (t1/2 for Cu5Mes5 being ca. 0.66 h) than in cyclohexane (t1/2 being ca. 56 h). The addition of electron-rich arenes to cyclohexane solutions of 1 greatly enhanced the rate of conversion of the pentamer to dimer. Addition of ligands to the solution containing the dimers allowed us to isolate complexes of different molecular complexity. The addition of THT (tetrahydrothiophene) to a THF solution of 1 resulted in the formation of the complex [Cu4Mes4THT2] (5). The results of the reactions of 1-3 with phosphines are reported and appear to be strongly dependent on the nature of the metal. PPh3 and dppe (Ph2PCH2CH2PPh2) stabilize the copper(I) dimer in solution, and subsequently they promote a ligand rearrangement with the formation of the corresponding cuprate. dppm (Ph2PCH2PPh2) reacts with 1 and 2 with the protolysis and elimination of the mesityl group to form [Cu3(Ph2PCHPPh2)3]·2C 7H8 (8) and [Ag3(Ph2PCHPPh2)3]·2C 7H8 (9), respectively. Complex 2 reacts with dppe in the same way as 1 or 3 depending on the nature of the solvent. Full characterization of the complexes was prevented by their thermal and photochemical instability. The reaction of phosphines PPh3, dppm, and dppe did not affect the [AuMes] functionality; in all three cases formation of the [P-Au-Mes] dicovalent gold(I) complexes [AuMesPPh3] (10), [Au2Mes2(μ-dppm)] (11), and [Au2Mes2(μ-dppe)] (12) was observed. The structures of six compounds have been determined. Crystallographic details for complexes 1, 2, 3, 5, 9, and 12 are as follows: Complex 1: space group P21/n (monoclinic), a = 16.094 (4) Å, b = 16.022 (4) Å, c = 19.259 (5) Å, β = 97.49 (3)°, V = 4924 (2) Å3, Z = 4, Dcalcd = 1.232 g cm-3. The final R factor was 0.10 for 1629 observed reflections. Complex 2: space group R3 (rhombohedral), a = b = c = 18.395 (3) Å, α = β = γ = 116.28 (2)°, V = 3038 (4) Å3, Z = 3, Dcalcd = 1.489 g cm-3. The final R factor was 0.062 (Rw = 0.064) for 1966 observed reflections. Complex 3: space group Pnma (orthorhombic), a = 21.864 (10) Å, b = 27.188 (11) Å, c = 8.951 (5) Å, V = 5321 (4) Å3, Z = 4, Dcalcd = 2.153 g cm-3. The final R factor was 0.052 (Rw = 0.050) for 2023 observed reflections. Complex 5: space group P1 (triclinic), a = 12.907 (3) Å, b = 20.624 (6) Å, c = 8.708 (2) Å, α = 102.14 (3)°, β = 107.38 (3)°, γ = 89.64 (3)°, V = 2159 (1) Å3, Z = 2, Dcalcd = 1.396 g cm-3. The final R factor was 0.057 (Rw = 0.062) for 3117 observed reflections. Complex 9: space group P21/n (monoclinic), a = 14.004 (2) Å, b = 23.632 (4) Å, c = 24.572 (4) Å, β = 101.66 (1)°, V = 7964 (2) Å3, Z = 4, Dcalcd = 1.384 g cm-3. The final R factor was 0.061 for 5695 observed reflections. Complex 12: space group P1 (triclinic), a = 11.700 (2) Å, b = 12.475 (2) Å, c = 7.647 (1) Å, α = 101.52 (1)°, β = 95.81 (1)°, γ = 109.55 (1)°, V = 1013.4 (3) Å3, Z = 1, Dcalcd = 1.650 g cm-3. The final R factor was 0.036 for 3659 observed reflections.
The optical properties of [Au2Ag2(C6F5)4(OCMe2)2]n (1) have been studied in the solid state at room temperature and at 77 K and in acetone solution (5 × 10-4 M). The crystal structure of 1, analyzed by X-ray diffraction, consists of polymeric chains formed by repetition of Au2Ag2 moieties linked through short gold−gold interactions. The emission profile observed for 1 in dilute acetone solution (5 × 10-4 M) is assignable to pentafluorophenyl localized ππ* excited states or from π-MMCT transitions, and in the solid-state arises from metal-centered (dσ*)1(pσ)1 or (dδ*)1(pσ)1 excited states. When the absorption and emission spectra of compound 1 in acetone are registered at different concentrations, they display a band that does not obey the Lambert−Beer law. This deviation is consistent with molecular aggregation in solution through gold−gold interactions, and a clear correlation between the emission wavelength and the structure of 1 in the solid state and in solution is shown. DFT calculations accord with the observed experimental behavior and show the nature of the orbitals involved in each transition.
Intermolecular van der Waals radii of the nonmetallic elements have been assembled into a list of "recommended" values for volume calculations. These values have been arrived at by selecting from the most reliable X-ray diffraction data those which could be reconciled with crystal density at 0°K. (to give reasonable packing density), gas kinetic collision cross section, critical density, and liquid state properties. A qualitative understanding of the nature of van der Waals radii is provided by correlation with the de Broglie wave length of the outermost valence electron. Tentative values for the van der Waals radii of metallic elements - in metal organic compounds - are proposed. The paper concludes with a list of increments for the volume of molecules impenetrable to thermal collision, the so-called van der Waals volume, and of the corresponding increments in area per molecule.
Four copper complexes with hydroxylated bipyridyl-like ligands, namely [Cu2(ophen)2] (1), [Cu4(ophen)4(tp)] (2), [Cu4(obpy)4(tp)] (3), and [Cu4(obpy)4(dpdc)]⋅2H2O (4), (Hophen=2-hydroxy-1,10-phenanthroline, Hobpy=6-hydroxy-2,2′-bipyridine, tp=terephthalate, dpdc=diphenyl-4,4′-dicarboxylate) have been synthesized hydrothermally. X-ray single-crystal structural analyses of these complexes reveal that 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy) ligands are hydroxylated into ophen or obpy during the reaction, which provides structural evidence for the long-time argued Gillard mechanism. The dinuclear copper(I) complex 1 has three supramolecular isomers in the solid state, in which short copper–copper distances (2.66–2.68 Å) indicate weak metal–metal bonding interactions. Each of the mixed-valence copper(i,ii) complexes 2–4 consists of a pair of [Cu2(ophen)2]+ or [Cu2(obpy)2]+ fragments bridged by a dicarboxylate ligand into a neutral tetranuclear dumbbell structure. Dinuclear 1 is an intermediate in the formation of 2 and can be converted into 2 in the presence of additional copper(II) salt and tp ligands under hydrothermal conditions. In addition to the ophen-centered π→π* excited-state emission, 1 shows strong emissions at ambient temperature, which may be tentatively assigned as an admixture of copper-centered d→s,p and MLCT excited states.
To verify whether attractive metallophilic interactions exist in the dimer-of-dimers [Cu(2)(ophen)(2)](2) (Hophen=1H-[1,10]phenanthrolin-2-one) (1), we designed and synthesized a series of such [M(2)L(2)](2) structures by varying the d(10) metal and/or the ligand (M=Cu(I) or Ag(I), L=ophen or obpy; Hobpy=1H-[2,2']bipyridinyl-6-one), and have successfully obtained three dimers-of-dimers: [Ag(2)(ophen)(2)](2).6 H(2)O (2), [Cu(2)(obpy)(2)](2) (3), and [Ag(2)(obpy)(2)](2).4.5 H(2)O.0.5 DMF (4). X-ray analyses of these structures show that interdimer M-M separations in [Ag(2)-(ophen)(2)](2) (3.199 A) are remarkably shorter than those in [Cu(2)(ophen)(2)](2) (3.595 A). Shorter interdimer M-M separations are found in the structures of [M(2)(obpy)(2)](2) (2.986 and 2.993 A in [Cu(2)(obpy)(2)](2), 3.037 to 3.093 A in [Ag(2)(obpy)(2)](2)), in which the pi systems are smaller than in the complexes with the ophen ligand. Detailed structural comparison of these dimers-of-dimers indicates that the interdimer, face-to-face pi-pi interactions repulse rather than support the interdimer metal-metal attractive interactions. This study also yields qualitative comparison of the strengths between argentophilic, cuprophilic, and face-to-face pi-pi interactions. DFT calculations on the four dimers-of-dimers further support the above deduction. The structure of a trimer-of-dimers [Ag(2)(obpy)(2)](3) (Ag-Ag 3.171 to 3.274 A) is further evidence that the oligomerization of the [M(2)L(2)] molecules is favored by stronger metallophilic and weaker face-to-face pi-pi interactions.
Introduction Historical PerspectiveThe Oxidation States of CopperThermal Stability and Bonding in Organocopper(I) CompoundsHomoleptic Organocopper Compounds CunRnHeteroleptic Organocopper Compounds Cun+mRnXmOrganocuprates Neutral Homoleptic and Heteroleptic OrganocupratesAnionic Homoleptic and Heteroleptic OrganocupratesLower- and Higher-order CyanocupratesConcluding Remarks Historical PerspectiveThe Oxidation States of CopperThermal Stability and Bonding in Organocopper(I) Compounds Neutral Homoleptic and Heteroleptic OrganocupratesAnionic Homoleptic and Heteroleptic OrganocupratesLower- and Higher-order Cyanocuprates
Chemists today are increasingly fascinated by gold’s unique position in the family of elements. In this review, the author
looks at important new results emerging from recent research in gold chemistry.
Arylcopper(I) compounds containing an oxazoline substituent in the position ortho to the Cu-C bond have been synthesized from the corresponding aryllithium compounds and CuBr. Depending on the order of addition this reaction afforded either a pure arylcopper(I) compound (slow addition of CuBr to the aryllithium reagent) or a mixture of arylcopper(I) and its CuBr adduct with [(RCu)2CuBr]2 stoichiometry (addition of aryllithium to a CuBr suspension). The new arylcopper(I) compounds were characterized by 1H NMR spectroscopy and cryoscopic molecular weight determinations in benzene, and for two of them the X-ray crystal structure has been determined. The structure of [Cu(MeOXL)]2 (MeOXL = 2-(4,4-dimethyl-2-oxazolinyl)-5-methylphenyl) (2b) (monoclinic crystals of space group P2/n, Z = 8, with a = 19.050 (1) Å, b = 6.671 (1) Å, c = 18.927 (1) Å, and β = 106.49 (1)°) shows a dimeric molecule containing a bridging 2-(2-oxazolinyl)aryl moiety, with two-center, two-electron carbon-copper bonds (Cu-C = 1.899 (5) Å). The oxazoline substituent is coordinated via the nitrogen with a Cu-N distance of 1.902 (4) Å. Such a two-center, two-electron bridge bonding mode is unprecedented in arylcopper chemistry. The CuBr adduct of 2b [Cu2(MeOXL)2CuBr]2 (triclinic crystals of space group P1, Z = 2, with a = 13.661 (3) Å, b = 19.154 (4) Å, c = 11.666 (5) Å, α = 95.46 (3)°, β = 92.49 (3)°, and γ = 110.49 (3)°) also shows a dimeric structure containing six copper atoms which form a distorted octahedron with four three-center, two-electron bridging aryl groups (Cu-C = 2.031 (3) Å (mean); Cu-Cu = 2.436 (3) Å (mean)) and two three-center, four-electron bridging bromine atoms (Cu-Br = 2.524 (3) Å (mean); Cu-Cu = 3.023 (4) Å (mean)). The oxazoline substituent is coordinated via the nitrogen atom (Cu-N = 1.968 (4) Å (mean)). Ullmann biaryl coupling reactions of the new organocopper(I) compounds with 2-iodopiperonal imine were little influenced by a hetero substituent in either the arylcopper(I) compound or the aryl iodide anchoring group. Moreover, since the addition of P(OMe)3 did not influence the coupling reaction, it can be concluded that "external" ligands do not have a critical role in these reactions. The results of this study show clearly the important influence that an ortho-chelating substituent (i.e. the 2-oxazolinyl group in the present compounds) can have on both the structural features and the reactivity of the arylcopper compounds.
The challenges and the opportunities in the field of crystal engineering were presented with the emphasis on supramolecular concepts. The supramolecular concepts were important for understanding the supramolecular isomerism and super structural diversity in the context of coordination polymers and organic molecular networks. These networks are based on the molecular components and the number and chemical type of components is restricted.
Cuprophilic interactions in neutral perpendicular model dimers of the type (CH3CuX)2 (X = OH2, NH3, SH2, PH3, N2, CO, CS, CNH, CNLi) were analyzed by ab initio quantumchemical methods. The basis set superposition error for the weakly interacting CH3CuX subunits is significant and is discussed in detail. A new correlation-consistent pseudopotential valence basis set for Cu. derived at the second-order Møller-Plesset level suppresses considerably the basis set superposition error in Cu-Cu interactions compared to the standard Hartree-Fock optimized valence basis set. This allowed the first accurate predictions of cuprophilicity, which has been the subject of considerable debate in the past. The dependence of the strength of cuprophilic interactions on the nature of the ligand X was addressed. The Cu-Cu interaction increases with increasing sigma-donor and pi-acceptor capability of the ligand and is approximately one-third of the well-documented aurophilic interactions. By fitting our potential-energy data to the Hershbach-Laurie equation, we determined a relation between the Cu-Cu bond length and the Cu-Cu force constant; this is important for future studies on vibrational behaviour. The role of relativistic effects on the structure and the interaction energy is also discussed. Finally we investigated cuprophilic interactions in (CH3Cu)4 as a model species for compounds isolated and characterized by X-ray diffraction.
X-ray crystallography reveals that individual molecules of Au(3)(NC(5)H(4))(3) self-associate through aurophilic interactions into two distinct structural motifs that involve both extended chains of molecules connected by pairwise Au.Au contacts and individual Au.Au contacts and discrete dimers linked by pairwise Au.Au contacts. The colorless or pale yellow crystals are remarkable for the formation of a distinct hourglass shape within the crystals that develops after months of standing in the atmosphere or after immersion in 4 M hydrochloric acid for a few days. The hourglass figures appear to result from the deposition of gold and are unusual in being formed by a chemical reaction within a crystal rather than as a result of dying the crystal during growth.
Crystallographic studies of yellow and colorless forms of [(C(6)H(11)NC)(2)Au(I)](PF(6)) show that they are polymorphs with differing, but close, contacts between the gold atoms which form extended chains. In the colorless polymorph the gold cations form linear chains with a short Au...Au contact (3.1822(3) A) indicative of an aurophilic attraction. The structure of the yellow polymorph is more complicated with four independent cations forming kinked, slightly helical chains with very short Au...Au contacts of 2.9803(6), 2.9790(6), 2.9651(6), and 2.9643(6) A. However, in the related compound, [(CH(3)NC)(2)Au(I)](PF(6)), each cation is surrounded by six hexafluorophosphate ions and there is no close Au...Au contact despite the fact that the isocyanide ligand has less steric bulk. The crystalline colorless and yellow polymorphs are both luminescent at 298 K, lambda(max): 424 nm (colorless) or 480 nm (yellow). Colorless solutions of the two polymorphs have identical absorption spectra and are nonluminescent at room temperature. Freezing solutions of [(C(6)H(11)NC)(2)Au(I)](PF(6)) produces intense luminescence which varies depending upon the solvent involved. Each polymorph melts to give a colorless but luminescent liquid which reverts to the yellow polymorph upon cooling.
The X-ray structure of (Tl[Au(C(6)Cl(5))(2)])(n), 1, consists of 1-D linear polymer chains parallel to the crystallographic z axis. The crystal structure of 1 has channels that run parallel to these chains with interatom distances in the range 3.231-4.076 A. There are holes in these channels with diameters as large as 10.471 A, which can accommodate a variety of solvents. Complex 1 displays reversible vapochromic emission and absorption spectral behavior when the solid is exposed to a variety of organic vapors such as acetone, acetonitrile, triethylamine, acetylacetone, tetrahydrothiophene, 2-fluoropyridine, tetrahydrofuran, and pyridine. Complex 1 is luminescent at room temperature and at 77 K in the solid state. UV excitation at 495 nm leads to an emission at 531 nm.
In the solid state, [Cu(NH3)Cl] forms a three-dimensional network with each Cu(I) ion being surrounded by three other Cu(I) centres in a trigonal-planar fashion [Cu...Cu = 2.979(1) A; cubic space group I2(1)3], whereas in [Cu(NH3)2]Br the cations establish infinite linear (Cu...Cu) chains spanning the crystal lattice [Cu...Cu = 2.931(1) A; monoclinic space group C2/c].
New dinuclear Au(I) complexes containing bridging thiouracilate and bis(diphenylphosphino)methane ligands have been synthesized and characterized structurally and spectroscopically. The compounds exhibit a unique behavior of solid-state luminescence tribochromism in which photoemission turns on upon gentle grinding of the sample and a sensitivity to pH in fluid solution. The emissive form in the solid state exhibits a bright blue or cyan emission upon irradiating at 375 nm. Structural studies show that the nonemissive form of the complexes has an extended helical ...Au...Au...Au... structure in the solid with weak aurophilic interactions, whereas the blue emissive form has a strong intermolecular aurophilic interaction in the solid that leads to an arrangement of dimers of dinuclear (Au2) complexes. Interconversion between the two forms can be carried out by either recrystallization for solid-state samples or by exposure to vapors of volatile acid or base for fluid solutions of the complexes.
A photophysical study is reported for the trinuclear copper(I) complex {[3,5-(CF3)2Pz]Cu}3. The neutral compound exhibits multicolor bright phosphorescent emissions both in the solid state and in solution. The emission can be tuned to multiple visible colors by controlling the temperature, solvent, and {[3,5-(CF3)2Pz]Cu}3 concentration, giving rise to luminescence thermochromism, luminescence solvatochromism, and a new optical phenomenon called "concentration luminochromism", respectively.
The nature of intermolecular interactions between dicoordinate Cu(I) ions is analyzed by means of combined theoretical and structural database studies. Energetically stable Cu(I).Cu(I) interactions are only found when the two monomers involved in the interaction are neutral or carry opposite charges, thus allowing us to speak of bonding between the components of the bimolecular aggregate. A perturbative evaluation of the components of the intermolecular interaction energies, by means the IMPT scheme of Stone, indicates that both the Coulombic and dispersion forces are important in determining the Cu(I).Cu(I) bonding interactions, because only a small part of that energy is attributable to Cu.Cu interactions, while a large component results from Cu.ligand interactions. The electrostatic component is the dominant one by far in the interaction between charged monomers, while in the interaction between neutral complexes, the electrostatic component is found to be of the same order of magnitude as the dispersion term. Bimolecular aggregates that have like charges are repulsive by themselves, and their presence in the solid state results from anion.cation interactions with ions external to this aggregate. In these cases, the short-contact Cu.Cu interactions here should be more properly called counterion-mediated Cu.Cu bonds.
- Nakamura
- Janiak