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ABSTRACT: The revitalized concept of "coordination at carbon" allows relationships between seemingly unrelated families of carbon-centered compounds to be discovered generating fascinating patchwork families of compounds. It is shown how olefins and cyclopropanes can be regarded as donors for carbon acceptors C(1) , C(2) , and C(3) . Through this approach, hydrocarbons such as spiropentane and dicyclopropylidene are found to be counterparts of the bis-ylidic carbodiphosphoranes and the corresponding mixed mono-ylidic systems.
Angewandte Chemie International Edition 12/2012; · 13.45 Impact Factor
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ABSTRACT: Recently accumulated experimental evidence for aurophilic interactions in and between molecular gold(I) compounds and the results of pertinent theoretical calculations are reviewed for the period from 2007 to mid-2011. The influence of the intra- and intermolecular bonding contacts between the closed-shell metal centres, Au-Au, on the molecular and crystal structures, and the consequences of these effects for the chemical and physical properties of gold compounds are summarized for the various classes of mono- and polynuclear systems. The literature survey builds on the contents of previous reviews and relates new experimental and theoretical findings to earlier observations (353 references).
Chemical Society Reviews 08/2011; 41(1):370-412. · 28.76 Impact Factor
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12/2009; , ISBN: 9780470682531
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12/2009; , ISBN: 9780470682531
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ABSTRACT: For a long time, π-complexes of gold in any of its oxidation states were considered elusive species of uncertain stoichiometry, low stability, and limited relevance. The recent upsurge of research activities in homo- and heterogeneous catalysis of reactions by gold and its compounds has now provided detailed and extensive information on almost all molecular prototypes with Au0, Au+, and Au3+ bound to alkenes, alkynes, and even arenes with low η2-hapticity (or, in special cases, η1 and η3). This extremely important progress in organogold chemistry is reviewed here with an emphasis on the hard experimental evidence and the structure and energy characteristics of gold π-coordination in molecular systems.
11/2009;
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ABSTRACT: There is now compelling experimental evidence for the existence of specific intra- and intermolecular bonding between seemingly closed-shell gold(I) centers (5d10) which manifests itself in all areas of gold chemistry. This "aurophilic interaction", which had not been predicted by conventional valence theory, was found to be associated with binding energies in some cases exceeding even those of strong hydrogen bonds and therefore to be highly significant in co-determining molecular structure and dynamics. In high-level theoretical treatments the attraction is rationalized as a "super van der Waals bonding" based on particularly strong relativistic, dispersion and correlation effects (critical review, 265 references).
Chemical Society Reviews 10/2008; 37(9):1931-51. · 28.76 Impact Factor
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ABSTRACT: SummaryA series of silylamines (aminosilanes) have been converted into their borane adducts using (tetrahydrofuran)- or (dimethyl sulfide)-borane as the BH3 source. Most of the adducts are unstable in solution and undergo rapid Si-N cleavage to give silanes and aminoboranes. Together with Me3SiNMe2-BH3 the complexes with aziridinyl- and azetidinylsilanes are the most stable. A crystal structure investigation of Ph3Si-N(CH2)2-BH3 has shown that the molecular geometry of the silylamine component of the adduct is virtually identical with that of the free silylaziridine with its steeply pyramidal configuration at nitrogen.
06/2008: pages 196 - 199; , ISBN: 9783527620777
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ABSTRACT: Compounds of the elements in the three triads of post-transition metals, Ga−In−Tl, Ge−Sn−Pb, and As−Sb−Bi, form in their low-valence states a variety of stable complexes with neutral hydrocarbons. This chemistry is reviewed starting from the early discoveries in the 19th century and including the most recent contributions.
05/2008;
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03/2006; , ISBN: 9780470862100
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03/2006; , ISBN: 9780470862100
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ABSTRACT: Lithium, sodium and potassium hydrogen bis-L-pyroglutamate [Li(L-pGlu)(L-pGluH)], [Na(L-pGlu)(L-pGluH)] and [K(L-pGlu)(L-pGluH)], respectively, have been prepared by reaction of aqueous solutions of the metal hydroxides with L-pyroglutamic acid in the molar ratio 1:2, or in methanol. Crystalline samples of the salts could be obtained by slow evaporation of solutions of the salts in methanol. In the solid state, Li(L-pGlu)(L-pGluH) adopts a chain structure with the lithium atoms arranged in double strands. Adjacent metal centers are bridged by the carboxylate groups of the L-pGlu− ligands. The L-pGluH ligands are attached to the metal centers through the amide oxygen atoms. Na(L-pGlu)(L-pGluH) forms a three-dimensional coordination polymer with two half-occupied sodium positions, one L-pGlu− and one L-pGluH ligand in the asymmetric unit. The carboxyl and carboxylate groups of the L-pGluH and the L-pGlu− ligands are bridging the sodium centers, giving rise to eight-membered rings, which consist of two sodium atoms, a carboxyl and a carboxylate group. The hydrogen atoms of the carboxyl group of the L-pGluH ligands are involved in strong hydrogen bonds between a carboxyl and an adjacent carboxylate oxygen atom. K(L-pGlu)(L-pGluH) adopts a layer structure with strands of potassium atoms. The metal centers are connected through bridging carboxyl and carboxylate groups of the L-pGluH and L-pGlu− ligands, respectively. The structure features eight-membered ring units comparable to those observed for Na(L-pGlu)(L-pGluH), again with the hydrogen atom of the carboxyl group engaged in a strong transannular hydrogen bond. The amide oxygen atoms of the L-pGlu− and the L-pGluH ligands are coordinated to the metal centers of adjacent coordination chains. The results of 1H- and 13CNMR investigations of aqueous solutions of the compounds indicate extensive electrolytic dissociation in dilute solutions.
Berichte der deutschen chemischen Gesellschaft 01/2006; 125(8):1829 - 1834. · 2.94 Impact Factor
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ABSTRACT: Two series of aminophosphonium ylides with reactive alkoxychlorosilyl substituents (R2N)3P=CHSi(OR')2Cl (1-8, R = Me, Et/R' = Me, Et, iPr, tBu) have been prepared by reaction of the aminophosphonium ylides (R2N)3P = CH2 with the corresponding dialkoxydichlorosilanes Cl2Si(OR')2. Substituent effects have been investigated by heteronuclear solution NMR studies of the nuclei 1H, 13C, 15N, 17O, 29Si, and 31P. These studies show an alternating shielding effect along the C–O–Si–C backbone. Further reactions of the chlorosilylated ylides with the aminomethylenephosphorane (Me2N)3P=CH2 lead to the formation of the bis-ylidic compounds [(Me2N)3P=CH]2Si(OR')2 (9, 10), which are also available in one-pot syntheses. The molecular structure of [(Me2N)3P=CH]2Si(OiPr)2 (9) has been confirmed by single-crystal X-ray diffraction. In the crystal the molecules have two ylidic carbon centers with planar configuration, which are bridged by a nearly tetrahedral silicon atom. Short P–C and Si–C distances indicate a stabilizing effect of the carbanionic centers.
Berichte der deutschen chemischen Gesellschaft 01/2006; 127(9):1599 - 1603. · 2.94 Impact Factor
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ABSTRACT: Strontium and barium l-aspartate are obtained by neutralization of aqueous solutions of l-aspartic acid with strontium or barium hydroxide, respectively. Slow crystallization from hot water affords the crystalline trihydrates, saturated solutions of which show pH values of 11.0 and 10.8 at ambient temperature. – The crystal structure of the two compounds has been determined by single crystal X-ray diffraction. The compounds are isomorphous (orthorhombic, space group P212121), and the structural parameters are very similar as expected from the small differences in the ionic radii of the two metals. – The cations are arranged in double strings parallel to the b axis. The l-aspartate dianions are bridging these double strings by chelating contacts of the two carboxylate groups with the metal atoms of different strings to give layers. While the α-carboxylate groups are only bidentate and associated with one metal atom each, the β-carboxylate oxygen atoms are also each bridging two adjacent metals of the neighbouring string. The three water molecules are all coordinated to the metal atoms, which attain coordination number 9. The amino groups are not engaged in metal coordination, but are part of a system of hydrogen bonds cross-linking the layers.
Berichte der deutschen chemischen Gesellschaft 01/2006; 123(8):1599 - 1602. · 2.94 Impact Factor
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ABSTRACT: Durch basenkatalysierte Hydrophosphorylierung von 1,3-Diphenylpropin mit Ph2PH wird 2-(Diphenylphosphino)-1,3-diphenyl-1-propen (1) erhalten, dessen Stereochemie durch Röntgenstrukturanalyse aufgeklrt wurde. Als Nebenprodukt werden auch geringe Mengen des regioisomeren 1-(Diphenylphosphino)-1,3-diphenyl-1-propens (2) isoliert. Deprotonierung von 1 mit n-BuLi und nachfolgende Umsetzung mit Chlordiphenylphosphan liefert das doppelt-phosphorylierte Produkt (R,S)-2,3-Bis(diphenylphosphino)-1,3diphenyl-1-propen (3). Durch Methylierung von 1 lßt sich das entsprechende Phosphoniumsalz 4 darstellen. Ebenfalls ausgehend von 1,3-Diphenylpropin wird nach doppelter Lithiierung, gefolgt von der Umsetzung mit Chlordiphenylphosphan, das erste 1,3′Diphosphino-substituierte Allen 5 synthetisiert. Aus diesem lßt sich durch starke Basen (RLi) eine Phosphinogruppe abspalten, wobei das Monophosphinoallen 6 entsteht. Oxidation sowie Addition von Schwefel und Selen ergeben die zugehörigen Dichalkogenide 5a–c, Hydrophosphorylierung von 5 führt auf einem anderen Weg zu 3.Contribution to the Synthesis and Structural chemistry of some Alkenyl- and Allenylphosphines1,3-Diphenylpropyne, obtained through an improved synthesis, undergoes base-catalyzed hydrophosphorylation with Ph2PH to give 2-(diphenylphosphino)-1,3-diphenyl-1-propene (1). The structure of 1 has been established by single-crystal X-ray diffraction. Regioisomeric 1-(diphenylphosphino)-1,3-diphenyl-1-propene (2) is a minor byproduct of the reaction. Metallation of 1 with n-BuLi followed by treatment with Ph2PCl yields (R,S)-2,3-bis(diphenylphosphino)-1,3-diphenyl-1-propene (3). Methylation of 1 with MeI gives the phosphonium salt 4. Double lithiation of PhCH2CCPh and reaction of the intermediate with two equivalents of Ph2PCl affords 1,3-bis(diphenylphosphino)-1,3-diphenylallene (5). This bisterminal phosphino-functionalized allene is converted into an oxide, sulfide, or selenide (5a–c) with the appropriate oxidant. Dephosphorylation of 5 with n-BuLi and subsequent hydrolysis lead to 1-(diphenylphosphino)-1,3-diphenylallene (6). Hydrophosphorylation of 5 with Ph2PH gives 3 by an alternative route.
Berichte der deutschen chemischen Gesellschaft 01/2006; 122(2):259 - 263. · 2.94 Impact Factor
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ABSTRACT: The synthesis and characterization of two complete series of benzyl(phenylsilyl)amines (PhH2Si)x(PhH2C)3 — xN, benzyl(p-tolylsilyl)amines (p-H3CC6H4H2Si)x(PhH2C)3 — xN, and of bis-(p-tolylsilyl)amine are described. The compounds have been prepared from the corresponding amines and chlorosilanes with triethylamine as the auxiliary base. Bis(phenylsilyl)(trimethylsilyl)amine, (PhH2Si)2NSiMe3 (10), was obtained by the reaction of lithium bis(phenylsilyl)amide with chlorotrimethylsilane. Crystal structure analyses reveal that dibenzyl(p-tolylsilyl)amine (7) and 10 contain planar nitrogen atoms. Heteronuclear NMR spectra (1H, 13C, 15N, and 29Si) have been measured for all compounds. The 15N chemical shifts are shown to be sensitive to variations of the geometry at the nitrogen atom. The coupling constants 1J(15N29Si) show a linear correlation with the N—Si bond lengths.
Berichte der deutschen chemischen Gesellschaft 01/2006; 126(9):2027 - 2032. · 2.94 Impact Factor
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ABSTRACT: Arsenic(III), Antimony(III), and Bismuth(III) Trihalide Complexes of [2.2.2]Paracyclophane: From Weak van der Waals Coordination to Strongly Directional π Complexation with Single or Double External η6 Coordination[2.2.2]Paracyclophane forms the adducts C24H24·AsCl3 (1), C24H24·(SbCl3)2·1/2 C6H6 (2), and C24H24·(BiCl3)3·C6H6 (3). For solutions in polar solvents NMR spectra indicate extensive dissociation and/or fluxionality. In the crystals adduct 1 features a weak addition of the AsCl3 molecule to one open side of a paracyclophane molecule with long intermolecular contacts approaching C3v symmetry. – Crystalline 2 shows SbCl3 coordination to two of the benzene rings of the hydrocarbon in a quasi-centered η6 mode, while one of the benzene rings remains uncoordinated. Chlorine-bridging between antimony atoms leads to tetrameric units (SbCI3)4 in the lattice. – In the bismuth compound 3 each benzene ring of the hydrocarbon is engaged in centroid (η6)π complexation, with the BiCl3 units crosslinked by chlorine bridges. The average of the Bi–ring distances (3.08,2.98, and 2.99 Å) is shorter than for the Sb–ring distances in 2 (3.047 and 3.050 Å), indicating stronger bonding. The crystal benzene is not coordinating.
Berichte der deutschen chemischen Gesellschaft 01/2006; 124(5):1089 - 1093. · 2.94 Impact Factor
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ABSTRACT: Triphenylphosphite has been converted into tris(phenylthiomethyl)phosphane (1) by reaction with LiCH2SPh/DABCO, and subsequently into the corresponding sulfide (2) and selenide (3) by treatment with elemental sulfur or selenium, respectively. Ligands 2 and 3 react with copper(I) halides CuX (X = Cl, Br, I) in polar organic solvents to give either 1:1 (X = Cl: 4, 7, X = Br: 5, 8 ) or 1:2 complexes (X = Br: 9, X = I: 6, 10). The crystal structures of five of these complexes have been determined by single crystal X-ray diffraction studies. All compounds of the type [(PhSCH2)3PS/Se]CuX (X = Cl, Br) form centrosymmetrical dinuclear complexes featuring a four-membered ring core Cu2[S/Se], fused to two five-membered rings Cu[S/Se]PCS through common trans edges. Only one of the three phenyl-thiomethyl functions is involved in coordination to a metal center. The compound [(PhSCH2)3PS](CuI)2 (6) is associated into a centrosymmetrical tetranuclear complex containing two four-membered rings (ICu2S) bridged via iodine atoms in 1,3-cis positions. The ligand is found to employ two of its PhSCH2 functions for metal coordination, giving rise to two five-membered rings fused to the four-membered rings via neighbouring edges. In all cases, therefore, the PS/Se functions of the ligands are the preferred donor sites, which are used for the building of bridgehead structural units of polynuclear complexes.
Berichte der deutschen chemischen Gesellschaft 01/2006; 130(1):105 - 110. · 2.94 Impact Factor
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ABSTRACT: The reaction of compounds (R3P) AuMe with diphenylphosphinous acid Ph2P(O)H affords methane and neutral complexes of the type (R3P(O)Ph2 (1a: R = Me; 1b: R = Ph, lc: R = o-Tol). 1a, b are obtained in high yield, but the yield of lc is lower owing to a side-reaction which leads to a different product: Ph2P(OH)–Au–P(O)Ph2 (2). The crystal structure of 1a was determined by a single-crystal X-ray diffraction study. The compounds is a monomer with a linear P–Au–P′ axis and the phosphane and phosphinite ligands in a staggered conformation. In solution (CHCl3, CH2Cl 2/) compounds 1a–c undergo a ligand redistribution, establishing equilibria that involve ionic isomers of the type [R3P)2Au]+ [Au-(P(O)Ph2)2]−, which are readily identified through their NMR data. The analogous reaction of (R3P)b AuMe with dimethylphosphite (MeO)2P(O)H gives methane and the corresponding dimethylphosphites of the type (R3P)AuP(O)(OMe)2 (3a: R = Me; 3b: R = Ph; 3c: R= o-Tol). The crystal structure of 3b has also been determined. It features a linear structure with an eclipsed conformation of the ligands. In polar solvents (CHCl3, methanol) there is again an eqilibrium between neutral and ionic isomers, the latter comprising bis(phosphane)gold cations [(R3P)2Au]+ and {Au[P(O)-(OMe)2]2)− anions, as confirmed by NMR spectroscopy and mass spectrometry.
Berichte der deutschen chemischen Gesellschaft 01/2006; 130(9):1333 - 1338. · 2.94 Impact Factor
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ABSTRACT: Reactions of (R3P)AuX (X = Cl, Br, I) with [(R3P)Au]+ BF−4 obtained from (R3P)AuCl and AgBF4 in tetrahydrofuran, lead to cationic binuclear gold(I) complexes of the general formula ([(R3P)Au]2X}+ BF−4. A number of chloro- (R = Ph, o-Tol, Mes, Bzl, Et), bromo- (R = Ph, o-Tol, Mes) and iodo-bridged (R = Ph, Mes) complexes of this type have been isolated and identified on the basis of their analytical and spectroscopic data. The crystal structure of bis[(triphenylphosphane)gold(I)]bromonium tetrafluoroborate was determined by single-crystal X-ray diffraction. The cations contain two-coordinate bromine atoms with an Au-Br-Au angle of 96.83(3)°.
Berichte der deutschen chemischen Gesellschaft 01/2006; 130(1):115 - 118. · 2.94 Impact Factor
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ABSTRACT: Crystalline Na2[Be(o-C6H4O2)2] · 5 H2O was prepared from beryllium hydroxide and a strongly alkaline aqueous solution of catechol. In an X–ray structure determination the complex was shown to feature dianions [Be(o-C6H4O2)2]2- with two chelating catechol ligands. The 9Be–NMR spectrum of an aqueous solution of the compound shows a singlet at δ 7.5. This signal is shifted considerably from the Beaq2+ reference and indicates persistence of the complexation of the metal ion by the catecholate ligands in alkaline aqueous solution. This result is important in the light of the ubiquitous availability of phenolic groups in many biomolecules, such as e.g. catecholamines.
Berichte der deutschen chemischen Gesellschaft 01/2006; 125(12):2701 - 2703. · 2.94 Impact Factor
