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Alcohol Amination with Aminoacidato Cp*Ir(III)-Complexes as Catalysts: Dissociation of the Chelating Ligand during Initiation
Abstract
The use of aminoacidato Cp*Ir(III)-complexes in catalytic alcohol amination reactions of primary and secondary alcohols with amines permits to carry out these transformations at very mild reaction conditions without the use of an additional base. Herein we discuss the fate of the chelating aminoacidato ligands upon initiation of Cp*Ir(III)-complexes from a mechanistic perspective. Catalyst initiation has been followed by NMR using isotopically labeled 13C,15N-glycinato complexes.
... Cell growth was determined by measuring the optical density (OD) at 540/630 nm with a Multiscan EX ELISA reader (Thermo Labsystems, Cheshire, WA, USA). Inhibition of cell growth (expressed as IC 50 : the inhibitory concentration that reduces by 50% the growth of the cells exposed to the tested compounds) was determined from the sigmoid curve where: inhibition = 100 − ((OD sample − OD medium control )/(OD cell control − OD medium control )) × 100 values were plotted against the logarithm of compound concentrations. Curves were fitted using GraphPad Prism software (2022, version 9.4.1, ...
... It was proven in our previous works that the longer bond lengths between the donor atoms and metal ion may indicate the lower aqueous stability of the complex [19,30]. To apply this observation in a broader scope, the M-N mono bond lengths of mixed-ligand half-sandwich Rh(III), Ru(II), Os(II) and Ir(III) complexes were collected and compared in Figure S27 [50][51][52][53][54][55][56][57][58][59][60][61]. The following general trend is visible in the bond length: M-imidazole < M-bim < M-Py < M-NH 3 . ...
... donor atoms and metal ion may indicate the lower aqueous stability of the complex [19,30]. To apply this observation in a broader scope, the M-Nmono bond lengths of mixedligand half-sandwich Rh(III), Ru(II), Os(II) and Ir(III) complexes were collected and compared in Figure S27 [50][51][52][53][54][55][56][57][58][59][60][61]. The following general trend is visible in the bond length: Mimidazole < M-bim < M-Py < M-NH3. ...
Cancer chemotherapeutics usually have serious side effects. Targeting the special properties of cancer and activation of the anticancer drug in the tumor microenvironment in situ may decrease the intensity of the side effects and improve the efficacy of therapy. In this study, half-sandwich Rh complexes are introduced, which may be activated at the acidic, extracellular pH of the tumor tissue. The synthesis and aqueous stability of mixed-ligand complexes with a general formula of [Rh(η5-Cp*)(N,N/O)(N)]2+/+ are reported, where (N,N/O) indicates bidentate 8-quinolate, ethylenediamine and 1,10-phenanthroline and (N) represents the releasable monodentate ligand with a nitrogen donor atom. UV-visible spectrophotometry, 1H NMR, and pH-potentiometry were used to determine the protonation constants of the monodentate ligands, the proton dissociation constants of the coordinated water molecules in the aqua complexes, and the formation constants of the mixed-ligand complexes. The obtained data were compared to those of the analogous Ru(η6-p-cymene) complexes. The developed mixed-ligand complexes were tested in drug-sensitive and resistant colon cancer cell lines (Colo205 and Colo320, respectively) and in four bacterial strains (Gram-positive and Gram-negative, drug-sensitive, and resistant) at different pH values (5–8). The mixed-ligand complexes with 1-methylimidazole displayed sufficient stability at pH 7.4, and their activation was found in cancer cells with decreasing pH; moreover, the mixed-ligand complexes demonstrated antimicrobial activity in Gram-positive and Gram-negative bacteria, including the resistant MRSA strain. This study proved the viability of incorporating releasable monodentate ligands into mixed-ligand half-sandwich complexes, which is supported by the biological assays.
... [10,27] Many of these transformations make it possible to avoid the preparation of unstable and difficult-to-prepare intermediates, for example, nitroso compounds,w hicht hus significantly facilitates the synthetic procedures. Complexes of ruthenium and iridium with PNP pincer, N-heterocyclic carbene (NHC), and related ligandsa re common catalysts for these reactions, [28][29][30][31] whereas alcoholo xidation to aldehyde is ak ey initial step of the reaction. Oncet he aldehyde is formed, intermolecular condensation, intramolecular cyclization,o rh ydrogen transfer can take place to give af inal product. ...
... Oncet he aldehyde is formed, intermolecular condensation, intramolecular cyclization,o rh ydrogen transfer can take place to give af inal product. [28][29][30][31] The scope of catalytic acceptorless dehydrogenative couplings with ruthenium and iridium molecular catalysts widensc ontinuously, and it has recently been expanded to the direct and selectivesynthesis of arylhydrazones from arylhydrazines and alcohols with the liberation of hydrogen gas (Scheme 7). [32] In the area of imine formation througho xidative coupling of alcohols and amines (Scheme8), main efforts are directed towards elaboration of cheaper and readily available catalysts. ...
In this review we attempted to answer the question: how to construct complex functionalized molecules with significant added value from cheap and readily available alcohols in the simplest and most efficient manner? Accordingly, recent developments (mainly from the last 5 years) in the field of one-pot multiple transformations of alcohols are overviewed in terms of the process simplification and optimization, sustainability, atom-, bond-, step- and redox- economy. A particular attention has been paid to chemo- and stereoselective transformations with specific formation of particular bonds and configurations, leaving other parts of substrates unchanged.
... Limbach et al. reported this cation as a triflate salt. 11 We obtained the crystal structure of 3 to confirm that the same trimetallic cluster was formed with different anions. The crystals of the BF 4 − salt described here are somewhat twinned and consist of a portion of both enantiomers. ...
Removal of chloride from Cp*Ir(glycinato)Cl in noncoordinating solvents with Ag[PF6] or Tl[PF6] leads to the formation of a closed octametallic loop of cations. The same loop also sequesters a number of PF6– counter anions. This is in contrast with reports that piano-stool complexes with amino acids form only trimetallic [Cp*Ir(aminoacidato)]3³⁺ moieties upon creating the cation. Cp*Ir(glycinato)Cl also forms a trimetallic compound as well as a octametallic compound, and the octametallic vs trimetallic formation appears to be dependent on the anion. The synthesis and characterization of the octametallic complex, as well as some monometallic and trimetallic compounds, are reported, including the X-ray crystal structures.
... Amines and their derivatives are manufactured massively by fine chemical industry every year, as they are important building blocks for the production of dyestuff, pesticides, and pharmaceuticals. (Muller and Beller, 1998, Tang and Zhang, 2003, Pohlki and Doye, 2003, Severin and Doye, 2007, Mueller et al., 2008 They are generally prepared by reductive aminations, (Storer et al., 2006, Gross et al., 2002 amination of aryl halides, (Hartwig, 2006, Buchwald et al., 2006 the direct amination of alcohols (Gunanathan and Milstein, 2008, Ye et al., 2014, Pingen et al., 2010, Imm et al., 2010, Oldenhuis et al., 2014, Woeckel et al., 2014 and hydroaminations (Muller and Beller, 1998, Mueller et al., 2008, Hartwig, 2008 of olefins. Beyond that, the catalytic reduction of nitriles are recognized as one of the most efficient and greenest one-step synthesis of these high-valued amine products. ...
A multicomponent nanocatalyst system was fabricated for the transfer hydrogenation of nitrile compounds. This catalyst system contains palladium, copper, and iron, which are supported on the magnetite nanospheres, and the loading of palladium could be at the parts per million level. Palladium and copper contribute to the transformation of nitrile, and the product distribution highly depends on the alloying of Fe to Cu. The nitriles could be converted to primary amine by the Pd-Cu catalyst in the absence of Fe, whereas in the presence of Fe the products are secondary amines with high selectivity. This could be attributed to the electronic modulation of iron to copper. A variety of nitriles have been transformed to the corresponding primary or secondary amines with high selectivity, and the TOF reaches 2,929 hr-1 for Pd. Furthermore, the catalyst could be recycled by an external magnetic field and reused five times without severe activity loss.
... As a result, the reaction is rarely used for producing higher-value amines. 2 As the reaction involves two redox steps (Scheme 1, steps a and c), catalysts known to facilitate dehydrogenation and hydrogenation processes are generally found to be effective for this reaction. [5][6] Homogeneous catalysts include Ir [7][8][9] and Ru 10 complexes, which can deliver high selectivity for the primary amine products with good tolerance towards the water by-product. ...
A highly selective synthesis of primary amines from alcohols and NH3 was achieved on using a commercially available Ni catalyst, without adding H2. Using a continuous flow reaction platform, the amination of aliphatic alcohols can be achieved in good yields and selectivities, as the accumulation of water by-product can be removed. Competitive formation of the nitrile side-product was suppressed when the catalyst is pre-reduced. Modes of catalyst deactivation was also briefly examined.
... [1] Recent development of transition-metal catalysis with primary amines such as CÀN coupling reactions [2a,b] and hydroaminations [2c] has expanded the range of potential applications for the synthesis of complex molecules. [3] Among several synthetic methods of primary amines, [4][5][6][7] the catalytic hydrogenation of nitriles is one of the most attractive approaches from the viewpoint of both green chemistry and the availability of starting materials. However, the reaction generally suffers from limited substrate scope and low selectivity. ...
Hydrogenation of nitriles to primary amines with heterogeneous catalysts under liquid-phase continuous-flow conditions is described. Newly developed polysilane/SiO2-supported Pd was found to be an effective catalyst and various nitriles were converted into primary amine salts in almost quantitative yields under mild reaction conditions. Interestingly, a complex mixture was obtained under batch conditions. Lifetime experiments showed that this catalyst remained active for more than 300 h (TON≥10 000) without loss of selectivity and no metal leaching from the catalyst occurred. By using this continuous-flow hydrogenation, synthesis of venlafaxine, an antidepressant drug, has been accomplished.
Continuous-flow hydrogenation is an important technology component to achieve multistep flow synthesis. Especially, hydrogenation of functional groups with high oxidation states such as nitrile, nitro, and carbonyl compounds are essential chemical transformations in my aldol-hydrogenation strategy (Scheme 3.1). To establish this method, I first focused on the hydrogenation of nitriles to primary amines as a target reaction.
Ammonia is the simplest molecule for the installation of nitrogen atom in organic compounds. It is abundantly available, economic and highly attractive from the point of atom economy for its use in organic synthesis, however, an highly challenging task for accessing the nitrogenous scaffolds through N‐H activation of ammonia. With the advancement of synthetic procedures, scientific community continually developing excellent reactions employing ammonia as a source of nitrogen for various types of amination reactions and accomplishing the synthesis of nitrogenous compounds. The present review will provide the recent developments in amination reactions employing ammonia as a nitrogen source at a single platform and serve the interested scientific fraternity in the field for better understanding and development.
Half‐sandwich iridium complexes bearing bidentate urea‐phosphorus ligands were found to catalyze the direct reductive amination of aromatic and aliphatic ketones under mild conditions at 0.5 mol.% loading with high selectivity towards primary amines. One of the complexes was found to be active in both the Leuckart‐Wallach (NH4CO2H) type reaction as well as in the hydrogenative (H2/NH4AcO) reductive amination. The protocol with ammonium formate does not require an inert atmosphere, dry solvents, as well as additives and in contrast to previous reports takes place in HFIP instead of methanol. Applying NH4CO2D or D2 resulted in a high degree of deuterium incorporation into the primary amine α‐position.
Two hybrid materials (1_TiO2 and 2_TiO2) were designed and prepared by anchoring novel [Cp*Ir(κ3‐O,N,O‐glyphosate)] (1; glyphosate=N‐(phosphonomethyl)glycine) and [Cp*Ir(κ3‐O,N,O‐glyphosine)] (2; glyphosine=N,N‐bis(phosphonomethyl)glycine) complexes onto rutile TiO2. Characterization in solution (NMR spectroscopy) and solid state (X‐Ray diffractometry) indicates that 1 and 2 are stabilized by the two arms of the glycine fragment, whereas they have (2) or can easily generate (1 and 2) a dandling phosphonate arm suitable for their anchoring on TiO2. As a matter of fact, they exhibit rather elongated Ir–OP (1: 2.1405 Å, 2: 2.142 Å) and short Ir–OC (1: 2.0784 Å, 2: 2.086 Å) and Ir–N (1: 2.155 Å, 2: 2.207 Å) bonds. NMR spectra of 2 show a dynamic process that exchanges the two phosphonate moieties, consistently with an easy –OP detachment from Ir. Both molecular and heterogenized species were tested as catalysts in water oxidation (WO) driven by NaIO4. 1 (TOF up to 96 min−1) and 2 (26 min−1) proved to be effective molecular catalysts; more importantly, 1_TiO2 and 2_TiO2 showed very high activity (TOF ∼200 min−1), which remained rather constant over seven successive runs, even if substantial leaching of the noble metal in solution occurred during the first catalytic tests. TON was very high and limited only by the amount of NaIO4 used. These results show the potentialities of mixed carboxylate/phosphonate ligands for the development of highly active water oxidation catalysts. The presence of amino acidate and methyl phosphonate functionalities in glyphosate and glyphosine were exploited to synthesize stable and suitable to be supported molecular Cp*Ir complexes. Their anchoring onto titania led to hybrid materials 1_TiO2 and 2_TiO2, which proved to be extremely active catalysts in water oxidation driven by NaIO4, despite some stability limitations.
Amide synthesis is one of the most important transformations in chemistry and biology. The direct use of ammonia for the incorporation of nitrogen functionalities in organic molecules is an attractive and environmentally benign method. We present here a new synthesis of amides by acceptorless dehydrogenative coupling of benzyl alcohols and ammonia. The reaction is catalyzed by a pincer complex of earth-abundant manganese in the presence of stoichiometric base, making the overall process economical, efficient and sustainable. Interesting mechanistic insights based on detailed experimental observations, indicating the crucial role of the base, are provided.
Within the green chemistry context, heterogeneous catalysis for the synthesis of N‐heterocycles from renewable resources using non‐precious metals has garnered great interest in terms of economic and environmental perspectives. Herein, we present a triazine functional hierarchical mesoporous organic polymer (HMOP) with nanorod morphology together with large BET surface area ∼1218 m2g‐1, huge pore volume > 6 mL.g‐1 and dual micro/mesopore architectures. Subsequent Cu‐coordination with nitrogen atoms of the HMOP provides a robust catalyst (Cu‐HMOP) to accomplish multi‐step cascade reactions for preparation of N‐heterocycles by different routes. For instance, the Cu‐HMOP efficiently catalyzes one‐pot sequential multi‐step oxidative dehydrogenative coupling of 2‐aminobenzyl alcohol with diverse aromatic ketones to afford corresponding quinolines in excellent isolated yields (up to 97%). Secondly, the present catalyst exhibits good aerobic oxidative dehydrogenation activity of amines to imines. Thirdly, for “click” reaction involving azides‐alkynes, the Cu‐HMOP produced quantitative yield for 1,4‐disubstituted 1,2,3‐triazole derivatives at room temperature using water as solvent. Verification of active metal leaching by a hot filtration test as well as reusability of the retrieved Cu‐HMOP catalysts shows a consistent activity in the multi‐component quinoline synthesis as model reaction.
In this report we attempt to describe and review the employment of α-amino acid ligands for the construction of metallic complexes. We focus our interest on the synthesis of discrete polynuclear Mn (n ≥ 3; M = d– f– and 3d–4f metal ions) complexes containing natural occurring or artificial α-amino acid ligands, and we briefly discuss their magnetic properties, where this is feasible. Polymeric species, coordination polymers and chains are not included in this review, due to space limitations. Finally, metallic clusters with macrocyclic ligands, and poly-peptides ligands are not included in this survey.
A series of benzoxazolyl and benzothiazolyl phosphine ligands 4a-4g were synthesized and characterized, which prepared from commercially available 2-aminophenol/2-aminobenzenethiol and 2-bromobenzaldehyde via cyclization and phosphination. The representative ligands 4c and 4e were determined by single-crystal X-ray diffraction. The corresponding iridium complexes could be generated in situ when [Cp*IrCl2]2 (Cp* = pentamethylcyclopentadienyl) encountered ligands. The molecular structures of complexes 5c and 5e were crystallographically characterized. The dihedral angles of N (1)-C (1)-C (8)-C (9) showed an increasing twist compared with the corresponding ligand. The iridium (III) catalysts were screened, [Cp*IrCl2]2/4a proved to be the optimal catalyst, which exhibited efficient catalytic activity toward versatile alkylations including ketones, secondary alcohols and amines with primary alcohols. Additionally, the synthesis of quinolines from ketones with 2-aminobenzyl alcohol by intermolecular cyclization and indole from 2-(2-aminophenyl)ethanol by intramolecular cyclization were achieved under the optimized conditions.
A series of ruthenium-cymene derivatives subjecting [Ru(η⁶-cymene)Cl2]2 and substituted bidentate N,O donor precursors have been synthesized and characterized. Reacting [Ru(η⁶-cymene)Cl2]2 with two equivalents the lithium salt of phenyl keto-amine ligands LiL1∼LiL3 resulted in the formation of [Ru(η⁶-cymene)(L)Cl] (1–3). Similarly, the reaction between [Ru(η⁶-cymene)Cl2]2 and two equivalents of LiL4 or NaL5 afforded compounds {Ru(η⁶-cymene)[L4)]Cl} (4) and [Ru(η⁶-cymene)(L5)Cl] (5). The ¹H NMR chemical shifts of aromatic protons of the cymene fragment for compounds 1–5 fell in the range δ 5.54–3.58, showing chemical shifts farther upfield than the corresponding protons of [Ru(η⁶-cymene)Cl2]2 due to the intramolecular ring current effect. The 2,6-diisopropylphenyl substituted pheny lketo-amine ligand of compound 3 shows a slow C-N bond rotation with the rotation rate constant at ca. 4.62 s⁻¹. The catalytic aminations of benzyl alcohol with benzylamine using compounds 1–3 as catalysts resulted in higher conversion than using compounds 4 and 5. Two products, PhCH = NCH2Ph and HN(CH2Ph)2 were detected, with PhCH = NCH2Ph being the major product. When benzyl alcohol was reacted with phenylamine in the presence of compounds 1–5, the conversions are all greater than 60% and PhCH = NPh was the major product. While sterically hindered 2,6-diisopropylaniline appeared in alcohol amination reactions in the presence of catalysts, no imine or amine products were detected.
Herein, we developed an efficient and selective nickel catalyzed mono-alkylation of various primary alcohols with aryl and hetero(aryl) amines together with diols and amino alcohol derivatives. Notably, the catalytic protocol consisting of earth abundant and non-precious NiBr2/L1 system enable the transformations in presence of hydroxyl, alkenes, nitrile and nitro-functionalities. As a highlight, we have demonstrated the alkylation of di-aniline, intramolecular cyclization to N-heterocycles, and functionalization of complex vitamin E, (±) α-tocopherol derivative. Preliminary mechanistic studies, re-vealed the participation of benzylic C-H bond in the rate determining step.
The synthesis of 2-alkylquinazolinones via iridium-catalyzed cyclization of o-aminobenzamides with unsaturated aldehydes has been accomplished. In the presence of [Cp*IrCl2]2, a series of desirable products were obtained in 77–91 % yields. This strategy is attractive due to high atom efficiency and the formation of water as the only side product.
The catalytic hydrogenation of nitriles to primary amines constitutes an environmentally benign and atom-economical methodology in synthetic organic chemistry. However, selective hydrogenation can be challenging, and usually elevated pressure and the use of various additives is requited. Herein the hydrogenation of aromatic and aliphatic nitriles to form primary amines catalyzed by ruthenium pincer complexes is described. The reactions are conducted at low H2 pressure, low catalytic loadings and, in case of a variety of benzonitriles, under neutral conditions and without any additives. Mechanistic insight is provided.
Synthesis of secondary and tertiary amines has been efficiently realized from the N-alkylation of amines with alcohols by means of heterogeneous bimetallic Pt-Sn/γ-Al2O3 catalyst (0.5 wt % Pt, molar ratio Pt:Sn = 1:3) through a borrowing hydrogen strategy. The Pt-Sn/γ-Al2O3 catalyst has exhibited very high catalytic activity towards a wide range of amines and alcohols, and can be conveniently recycled without Pt metal leaching. The present protocol was applied for the synthesis of N-phenylbenzylamine in 96% isolated yield from aniline and benzyl alcohol on a 2.1 kilogram scale of the substrates, demonstrating its potential applicability for higher-order amine synthesis.
The catalytic mechanism for the multi-alkylation of benzyl alcohols with ammonia catalyzed by the water-soluble catalyst, [Cp?IrIII(NH3)3][I]2, is computationally investigated by density functional theory (DFT). Three possible active catalysts based on various ligands, NH3, I, and H2O were investigated for the first catalytic cycle and the active catalyst with an ammine ligand is the best one. For the three interrelated and succession catalytic cycles (I, II, and III), each catalytic cycle consists of three stages: (stage I) the oxidation of the alkoxide ligand to free benzaldehyde; (stage II) the dehydration coupling between benzaldehyde and amine-reactant without the participation of the metal catalyst; (stage III) the reduction of imine by a hydride intermediate to give an amine-product. The three catalytic cycles have the same stage I, where the ?-H elimination step is the highest point of the profile. The transfer hydrogenation step of stage III is believed to be the rate-determining step of every catalytic cycle. Remarkably, for the three catalytic cycles, the active barrier of the key reductive hydride transfer gradually increases due to both electric and steric effects induced by the adding of the benzyl ring of the amine-reactant. Our computational results are in good agreement with the experimental outcomes of the reaction.
Benzylamines play a prominent role in numerous pharmaceutically active compounds. Thus, the development of novel, sustainable catalytic methodologies to provide access to these privileged structural motifs is of central importance. Herein we describe a systematic study for the construction of a large variety of benzylamines using a well-defined homogeneous iron complex. The methodology consists of the direct coupling of readily available benzyl alcohols with simpler amines through the borrowing hydrogen methodology, producing a variety of substituted secondary and tertiary benzylamines in moderate to excellent yields for the first time with an iron catalyst. Notably, we explore the versatility of this methodology in the one-pot synthesis of nonsymmetric tertiary amines, sequential functionalization of diols with distinctly different amines, and the synthesis of N-benzyl piperidines via various synthetic pathways. In addition, direct conversion of the renewable building block 2,5-furan-dimethanol to pharmaceutically relevant compounds is achieved.
The catalytic hydrogenation of nitriles to primary amines represents an atom-efficient and environmentally benign reduction methodology in organic chemistry. This has been accomplished in recent years mainly with precious-metal-based catalysts, with a single exception. Herein, the first homogeneous cobalt-catalyzed hydrogenation of nitriles to primary amines is reported. Several (hetero)aromatic-, benzylic- and aliphatic- nitriles undergo hydrogenation to the corresponding primary amines in good to excellent yields under the reaction conditions.
Several new bisbenzoxazolyl iridium(III) complexes have been synthesized and characterized through X-ray crystallography. These complexes exhibit excellent catalytic activity in C–C and C–N bond formation reactions from the alkylation of amine with amine, amine with alcohol, ketone with alcohol, and alcohol with alcohol through a borrowing hydrogen reaction. Moreover, these iridium(III) complexes are effective catalysts for the alkylation of amine with alcohol and ketone with alcohol under solvent-free conditions. The catalytic activity of these complexes is greatly enhanced by noncoordinating, while the experiments have excluded the possibility of a “silver effect” (bimetallic catalysis or silver-assisted metal catalysis) from the experiments.Keywords: C−C coupling; C−N coupling; solvent-free; iridium complex; noncoordinating anion
Silica supported palladium NiXantphos complex is reported as an efficient and a high turnover heterogeneous catalyst for the N-alkylation of amines and the α-alkylation of ketones using readily available alcohols under neat conditions at 120 – 140 oC following hydrogen borrowing strategy. The catalyst is easily separable and offers negligible amount of palladium leaching (<0.01 ppm). A high turnover number of about 46000 for the N-alkylation of amines and 4400 for the α-alkylation of ketones were achieved in the respective single batch reactions. The catalyst is recyclable up to four times without appreciable change in catalytic performance.
A highly robust immobilized [Cp*IrCl2]2 precatalyst on Wang resin for transfer hydrogenation, which can be recycled up to 30 times, was studied using a novel combination of X-ray Absorption Spectroscopy (XAS) at Ir L3-edge, Cl K-edge and K K-edge. These culminate in an in situ XAS experiments which links structural changes of the Ir complex with its catalytic activity and its deactivation. Mercury poisoning and 'hot filtration' experiments ruled out leached Ir as the active catalyst. Spectroscopic evidence indicates the exchange of one chloride ligand with an alkoxide to generate the active pre/catalyst. The exchange of the second chloride ligand, however, leads to a potassium alkoxide-iridate species as the deactivated form of this immobilized catalyst. These findings could be widely applicable to the many homogeneous transfer hydrogenation catalysts with Cp*IrCl substructure.
Transition metal-catalyzed substitution of alcohols by N-nucleophiles (or N-alkylation of amines and related compounds with alcohols) avoids the use of alkylating agents by means of borrowing hydrogen (BH) activation of the alcohol substrates. Water is produced as the only by-product, which makes the "BH" processes atom-economic and environmentally benign. Diverse types of homogeneous organometallic and heterogeneous transition metal catalysts, and substrates such as N-nucleophiles including amines, amides, sulfonamides and ammonia, and various alcohols, can be used for this purpose, demonstrating the promising potential of "BH" processes to replace the procedures using traditional alkylating agents in pharmaceutical and chemical industries. Borrowing hydrogen activation of alcohols for C-N bond formation has recently been paid more and more attention, and a lot of new and novel procedures and examples have been documented. This critical review summarizes the recent advances in "BH" substitution of alcohols by N-nucleophiles since 2009. "Semi-BH" N-alkylation processes with or without an external hydrogen acceptor are also briefly presented. Suitable discussion of the "BH" strategy provides new principles for establishing green processes to replace the relevant traditional synthetic methods for C-N bond formation.
A highly efficient C-C bond formation has been developed through the cross-coupling of primary and secondary alcohols. The corresponding functionalized ketones were obtained with iridium-CNP complex as a catalyst through the borrowing hydrogen strategy. The present methodology provides an easy alternative method to aldol reaction derivatives. More importantly, the complexes were also effective catalysts for the alkylation of an aromatic amine with a tertiary alkyl amine.
Reactions of L-tert-Leucine (tert-butylglycine), tert-leucine methyl ester, GlyValOMe, and Leu- AlaOMe with the chloro-bridged complexes [Cp*IrCl 2 ] 2 , [(p-cymene)RuCl 2 ] 2 or [(C 6 Me 6 )RuCl 2 ] 2 in the presence of NaOMe give the complexes [Cp*Ir(Cl)NH 2 CH(R)CO 2 ] (1), [(p-cymene)Ru(Cl)- NH 2 CH(R)CO 2 ] (2), Cp*Ir(Cl 2 )[NH 2 CH(R)CO 2 Me] (5), {(C 6 Me 6 )Ru(Cl)[NH 2 CH 2 CONHCH(R)- CO 2 Me]} ⁺ Cl ⁻ (6), [Cp*Ir(Cl)NH 2 CH 2 CONCH(R)CO 2 Me] (7), [Cp*Ir(Cl)NH 2 CH(CH 2 CHMe 2 )- CONCH(R)CO 2 Me)] (8), and Cp*Ir(Cl 2 )[NH 2 CH 2 CONHCH(R)CO 2 Me) (9).
With pentaglycine the complexes [Cp*Ir(Cl 2 )(pentaglycinate ⁺ Na ⁺ )] (10) and [(C 6 Me 6 )Ru(pentaglycineOMe- H ⁺ )] (11) could be isolated. Coordination of one equivalent of the S-protected tripeptide glutathione to [Cp*Ir(Cl)] and to [(C 6 Me 6 )Ru(Cl)] was observed. Some in situ prepared (p-cymene)Ru complexes with deprotonated dipeptide esters were tested as catalysts and the complex [(p-cymene)Ru(Cl)(NH 2 CH(CHMeEt)NCH (CHMe 2 )CO 2 tert-Bu)] gave a yield of 73% and moderate entantiomeric excess (36% ee) in the transfer hydrogenation of acetophenone to 2-propanol.
A description of the ab initio quantum chemistry package GAMESS is presented. Chemical systems containing atoms through radon can be treated with wave functions ranging from the simplest closed-shell case up to a general MCSCF case, permitting calculations at the necessary level of sophistication. Emphasis is given to novel features of the program. The parallelization strategy used in the RHF, ROHF, UHF, and GVB sections of the program is described, and detailed speecup results are given. Parallel calculations can be run on ordinary workstations as well as dedicated parallel machines. © John Wiley & Sons, Inc.
COSMO-RS, a general and fast methodology for the a priori prediction of thermophysical data of liquids is presented. It is based on cheap unimolecular quantum chemical calculations, which, combined with exact statistical thermodynamics, provide the information necessary for the evaluation of molecular interactions in liquids. COSMO-RS is an alternative to structure interpolating group contribution methods. The method is independent of experimental data and generally applicable. A methodological comparison with group contribution methods is given. The applicability of the COSMO-RS method to the goal of solvent screening is demonstrated at various examples of vapor–liquid-, liquid–liquid-, solid–liquid-equilibria and vapor-pressure predictions.
We present two new hybrid meta exchange- correlation functionals, called M06 and M06-2X. The M06 functional is parametrized
including both transition metals and nonmetals, whereas the M06-2X functional is a high-nonlocality functional with double
the amount of nonlocal exchange (2X), and it is parametrized only for nonmetals.The functionals, along with the previously
published M06-L local functional and the M06-HF full-Hartree–Fock functionals, constitute the M06 suite of complementary functionals.
We assess these four functionals by comparing their performance to that of 12 other functionals and Hartree–Fock theory for
403 energetic data in 29 diverse databases, including ten databases for thermochemistry, four databases for kinetics, eight
databases for noncovalent interactions, three databases for transition metal bonding, one database for metal atom excitation
energies, and three databases for molecular excitation energies. We also illustrate the performance of these 17 methods for
three databases containing 40 bond lengths and for databases containing 38 vibrational frequencies and 15 vibrational zero
point energies. We recommend the M06-2X functional for applications involving main-group thermochemistry, kinetics, noncovalent
interactions, and electronic excitation energies to valence and Rydberg states. We recommend the M06 functional for application
in organometallic and inorganometallic chemistry and for noncovalent interactions.
Various contracted Gaussian basis sets for atoms up to Kr are presented which have been determined by optimizing atomic self‐consistent field ground state energies with respect to all basis set parameters, i.e., orbital exponents and contraction coefficients.
β-Phenylalanine forms with chloro bridged complexes the chiral N, O-chelates Cp*Ir(Cl)(NH 2 CH(Ph)CH 2 CO 2 ) and (p-cymene)Ru(Cl)(NH 2 CHPhCH 2 CO 2 ) as mixture of two diastereoisomers. Similarly the palladium(III) and platinum(II) complexes (Et 3 P)(Cl)M(NH 2 CH(Ph)CH 2 CO 2 ) (M = Pd, Pt) were obtained. Schiff base complexes (arene)(Cl)M(O 2 CC(R)=N-CH(R)CH(R)CH 2 CO 2 CH 3 ) (arene = Cp*, p-cymene; M = Ir, Ru) were synthesized from the chloro-bridged compounds, 2-oxocarboxylates and β-alanine or β-phenylalanine methylester. The Cp*Ir complex with a tridendate dianionic Schiff base generated from pyruvate and β-phenylalaninate is obtained as a single isomer. Cp*Ir(Cl) forms a complex with an N, O-bidentate Schiff base ligand from glycinate and acetylacetic ethyl ester.
Ranging from hydrogenation to hydroamination, cycloadditions and nanoparticles, this first handbook to comprehensively cover the topic of iridium in synthesis discusses the important advances in iridium-catalyzed reactions, namely the use of iridium complexes in enantioselective catalysis. A must for organic, complex and catalytic chemists, as well as those working with/on organometallics.
β-Phenylalanine forms with chloro bridged complexes the chiral N,O-chelates Cp*Ir(Cl)(NH2CH(Ph)CH2CO2) and (p-cymene)Ru(Cl)(NH2CHPhCH2CO2) as mixture of two diastereoisomers. Similarly the palladium(III) and platinum(II) complexes (Et3P)(Cl)M(NH2CH(Ph)CH2CO2) (M = Pd, Pt) were obtained. Schiff base complexes (arene)(Cl)M(O2CC(R)=N-CH(R)CH(R)CH2CO2CH 3) (arene = Cp*, p-cymene; M = Ir, Ru) were synthesized from the chloro-bridged compounds, 2-oxocarboxylates and β-alanine or β-phenylalanine methylester. The Cp*Ir complex with a tridendate dianionic Schiff base generated from pyruvate and β-phenylalaninate is obtained as a single isomer. Cp*Ir(Cl) forms a complex with an N,O-bidentate Schiff base ligand from glycinate and acetylacetic ethyl ester.
Reactions of chloro bridged complexes with sarcosinate, N-methylalaninate and ethylenediamine-N,N′-diacetate give the halfsandwich complexes [Cp*M(Cl)(NHMeCHRCO2)] (M = Ir, Rh; R = H, Me), [(p-cymene)Ru(Cl)(NHMeCHRCO2)] (R = H, Me) with chiral metal and N-atoms, the palladium and platinum complexes [(R 3P)(Cl)M(NHMeCHR′CO2)] (M = Pd, Pt; R′ = H, Me) and the dinuclear compounds [(Cl)(R3P)M-(O2CCH 2NHCH2CH2NHCH2CO 2)M(PR3)(Cl)]. The possible diastereoisomers of these complexes are discussed on the basis of their 1H, 13C, and 31P NMR spectra.
The mononuclear neutral chlorides [(η-ring)M(Aa)Cl] ((η-ring)-M = (η5-C5Me5)Rh, (η5-C5Me5)Ir, (η6-p-MeC6H4i(Pr)Ru; Aa = α-amino acidate) were treated with AgBF4 to yield the corresponding new chiral trimers [{(η-ring)M(Aa)}3](BF4)3. Compounds [{(η5-C5Me5)Ir(Ala)}3](BF 4)3 (1b) and [{(η6-p-MeC6H4iPr)Ru(L-Pro)} 3](BF4)3 (6c) were characterised by X-ray diffraction. Trimerisation takes place by chiral self-recognition: the trimers RMRMRM (ρ isomer) or SMSMSM (o isomer), which have equal configuration at the metal centre, were the only diastereomers detected. In solution, a diastereomerisation process between both isomers occurs, where the equilibrium constant depends on the solvent, amino acidate, and metal. The different localisation of the polar groups (NH or NH2 moieties) on the molecular surface of the two diastereomers (ρ and σ) provides a qualitative explanation for the different diastereomer stability observed in solution. The new chiral trimers catalyse the reduction of unsaturated aldehydes to unsaturated alcohols by hydrogen transfer from aqueous sodium formate and the reduction of acetophenone by hydrogen transfer from 2-propanol with up to 75 % ee.
The structure of the title complex consists of [Ir 3 (C 5 Me 5 ) 3 (L-prolinate) 3 ] ³⁺ complex cations and CF 3 SO 3 ⁻ anions. Each iridium atom is coordinated in a distorted tetrahedral manner by one cyclopentadienyl group, two carboxylate O atoms and the prolinate N atom. The iridium atoms are bridged by the carboxylate groups. Each of the three stereogenic iridium atoms has the same (S) configuration, i. e. the trimerization of the [Ir(C 5 Me 5 )(L-prolinate)] ⁺ fragment occurs with chiral self recognition.
In this Minireview, the synthesis of amines by the amination of alcohols, by means of the so-called borrowing hydrogen methodology, is presented. Compared to other synthetic methodologies for the synthesis of amines, these transformations are highly attractive because often alcohols are readily available starting materials, some of them on a large scale from renewable sources. In addition, the amination of alcohols produces water as the only by-product, which makes the process potentially environmentally benign. Already today, lower alkyl amines are produced in bulk by the chemical industry with this synthetic method. In particular, the recent progress applying organometallic catalysts based on iridium, ruthenium, and other metals will be discussed. Notable recent achievements include the conversion of challenging substrates such as diols, the development of recyclable catalysts, milder reaction temperatures, and the direct alkylation of ammonia or its equivalents with alcohols.
Diastereomers (SIr,SN,SC)- and (RIr,SN,SC)-[(η5-C5Me5)Ir(L-prolinate)(CCCMe3)] have been prepared and the structure of the later determined by X-ray diffraction methods.
Diastereomeric mixtures of epimers at metal of the α-amino carboxylate compounds [(ηn-ring)M(Aa)Cl] [(ηn-ring)M = (η5-C5Me5)Rh(III), (η5-C5Me5)Ir(III), (η6-p-MeC6H4iPr)Ru(II); Aa = α-amino carboxylate] can be readily prepared from the corresponding acetylacetonate compounds [(ηn-ring)M(acac)Cl]. In general, even below 0 °C, these complexes epimerise at the metal. The absolute configuration at the metal has been determined by X-ray diffractometric methods and NMR and CD spectroscopies. The molecular structures of the complexes [(η5-C5Me5)M(Aa)Cl] [M(Aa) = Rh(l-Pro), Ir(l-Pro), Rh(MePro), Ir(MePro)] and [(η6-p-MeC6H4iPr)Ru(Aa)Cl] (Aa = Hyp, MePhe, MePro) are reported. Related iodide complexes, [(ηn-ring)M(Aa)I], can be prepared from the corresponding chlorides by halogen metathesis.
The synthesis and characterization of optically active amino acidato complexes of the types [(C5Me5)M(aa)Cl], [(p-cymene)Ru(aa)Cl], [(C5Me5)M(aa)(PPh3)]BF4, and [(p-cymene)Ru(aa)(PPh3)]BF4 (M = Rh, Ir; Haa = l-alanine, l-proline), in which the metal is a chiral centre, are reported. The cationic species were prepared via the solvato-complexes [(C5Me5)M(aa)(MeOH)]+ and [(p-cymene)Ru(aa)(MeOH)]+, which epimerize rapidly on the 1H NMR time scale. The crystal structure of the complex [(C5Me5)Ir(pro)Cl] is reported; the asymmetric unit contains two independent molecules differing in the configuration at the metal.
A new effective catalytic system consisting of [Cp*IrCl2]2/K2CO3 (Cp*=pentamethylcyclopentadienyl) for the N-alkylation of primary amines with alcohols has been developed. As an example, the reaction of aniline with benzyl alcohol in the presence of [Cp*IrCl2]2 (5.0 mol%Ir) and K2CO3 (5.0 mol%) in toluene at 110°C for 17 h gave benzylaniline in an isolated yield of 88%.
Metal Complexes of Biologically Important Ligands, LIII. – Chiral Half-Sandwich Complexes of Rhodium(III), Iridium(III), Iridium(I), and Ruthenium(I1) with a-Amino Acid Anions
The chloro-bridged metal compounds Cp*(Cl)M(μ-Cl)2M(Cl)-Cp* (M = Rh, Ir; Cp* = η5-C5Me5), (η6-C6H6)(Cl)
A recent development for the efficient and environmentally friendly synthesis of aliphatic amines is the transition-metal-catalyzed redox-neutral coupling of an alcohol and an amine, generally referred to as a "borrowing hydrogen" reaction. In this work, we describe the first kilogram-scale application of this technology in the synthesis of PF-03463275, a GlyT1 inhibitor developed for the treatment of schizophrenia. Using (Cp*IrCl(2))(2) the reaction has been optimized to achieve catalyst loadings lower than 0.05 mol % iridium (S/C >= 2000) while retaining reasonable reaction times (< 24 h). Water and a tertiary amine are essential for high catalytic activity, resulting in dramatically increased reaction rates compared to existing literature protocols. Methods for iridium removal are also described.
The complete analysis of the 1H NMR spectra of [(C5Me5)Ir(glycinate)Cl] and [(C5Me5)Ir(N-methyl- glycinate)Cl] provide information for the conformational analysis of the five-membered N—C—C—O—Ir ring. A Karplus relationship has been established for these metallacycles [3J(H,H) = 8.9 cos2 ϕ-1.0 cos ϕ+0.8].
The kinetic resolution of amines using a novel iridium based catalyst coupled with an enzyme catalysed step is achieved on a large scale with high yields and ee. (c) 2006 Elsevier Ltd. All rights reserved.
[Cp*Ir(Pro)Cl] (Pro = prolinato) was identified among a series of Cp*-iridium half-sandwich complexes as a highly reactive and selective catalyst for the alkylation of amines with alcohols. It is active under mild conditions in either toluene or water without the need for base or other additives, tolerates a wide range of alcohols and amines, and gives secondary amines in good to excellent isolated yields.
We assess various approximate forms for the correlation energy per particle of the spin-polarized homogeneous electron gas that have frequently been used in applications of the local spin density approximation to the exchange-correlation energy functional. By accurately recalculating the RPA correlation energy as a function of electron density and spin polarization we demonstrate the inadequacies of the usual approximation for interpolating between the para- and ferro-magnetic states and present an accurate new interpolation formula. A Padé approximant technique is used to accurately interpolate the recent Monte Carlo results (para and ferro) of Ceperley and Alder into the important range of densities for atoms, molecules, and metals. These results can be combined with the RPA spin-dependence so as to produce a correlation energy for a spin-polarized homogeneous electron gas with an estimated maximum error of 1 mRy and thus should reliably determine the magnitude of non-local corrections to the local spin density approximation in real systems.
The structure of coordinatively unsaturated (16-electron) two-legged piano stool complexes is analyzed with the extended Hückel methodology as well as with density functional theory. Pyramidal, and thus potentially chiral at the metal, geometries are predicted to be preferred for complexes bearing ligands like CO, CS, or NO+, containing low-lying π-acceptor orbitals, as well as in the case of electropositive strong σ donors, e.g., for silyl ligands. In all cases, however, the computed inversion barriers are low (<15 kcal mol-1). A minimum was located for an η2-coordination of an acyl ligand in [CpFe(acyl)NO]+, which may account for the stereospecific ligand substitution in acyl-containing systems. The ground-state geometry of the isoelectronic series [(ηn-CnHn)M(CO)2] (M = Fe, Mn, Cr, V; n = 4−7) is probed as a function of ring size and metal center.
Air-stable Ir and Ru complexes of a chelating pyrimidine-functionalized N-heterocyclic carbene were synthesized. The complexes were characterized by NMR spectroscopy and single-crystal X-ray diffraction and were found to be catalytically active for transfer hydrogenation, β-alkylation of secondary alcohols with primary alcohols, and N-alkylation of amines with primary alcohols. Notably, the Ir complexes were found to catalyze the N-alkylation of amines using the mild base NaHCO3.
A new pentamethylcyclopentadienyl-functionalized N-heterocyclic carbene ligand (Cp*-NHCMe) has been prepared and coordinated to iridium upon reaction with [Ir(μ-Cl)(cod)]2. The chiral Ir complex is obtained as a racemic mixture of the two possible enantiomers, and its crystal structure is described. The new compound shows high catalytic activity toward transfer hydrogenation, β-alkylation of secondary alcohols with primary alcohols, and amination of primary alcohols.
Amino acid derivatives bearing an electron-withdrawing group Z on N (Z = tosyl, CO2-CH(2)Ph, or acetyl) serve as (N,O)-chelating, dianionic ligands to the fragment Cp*Ir. Six such complexes have been prepared, all of them coordinatively unsaturated yet air-stable. The structure of the N-tosylglycine derivative C19H24IrNO4S (5a) was analyzed at 20 degrees C. A planar chelate ring was revealed, and relatively short Ir-N and Ir-O bonds suggested stabilization of unsaturated Ir by pi-donation. Crystals of the (R)-N-tosylphenylglycine complex C25H28IrNO4S (5f) were monoclinic. Some distortion of the chelate ring was seen, and both aryl rings were syn, the angle between their mean planes being 19 degrees. Within seconds, red solutions of the unsaturated complexes 5 turn yellow on addition of ligands such as phosphines, CO, and primary aliphatic or heterocyclic amines. Ligands add to chiral complexes so as to place the amino acid side chain R and Cp* cis to each other on the metallacycle, suggesting preferred approach of the ligand to 5 from the side opposite R. For one PMe(3) adduct this was shown to be the result of kinetic control (greater than or equal to 50:1 selectivity at 25 degrees C) and thermodynamic control (40:1 selectivity after equilibration at 90 degrees C, half-life = 5 h). PPh(3) and amines exchange within minutes at 25 degrees C. The stereoselectivity of ligand addition was highest for smaller ligands. Comparing this result and previous work suggests that steric interactions between added ligand and the amino acid side chain R determine diastereoselectivity.
The synthesis and characterization of optically active amino acidate alkynyl complexes of general formula [(ηn-ring)M(aa)(CCR)] ((ηn-ring)M = (η5-C5Me5)Rh; aa = l-prolinate (Pro); R = CMe3 (1), SiMe3 (2); (ηn-ring) M = (η5-C5Me5)Ir; aa = Pro; R = CMe3 (3), SiMe3 (4); aa = N-methyl-l-prolinate (MePro); R = CMe3 (5), SiMe3 (6); (ηn-ring)M = (η6-p-MeC6H4iPr)Ru; aa = l-alaninate (Ala); R = Ph (7), CO2Me (8); aa = Pro; R = Ph (9), CO2Me (10)) are reported. The crystal structures of (RIr,SC,SN)-3b and (SIr,SC,SN)-5 were determined by X-ray analysis. Both molecular structures exhibit analogous pseudo-octahedral arrangements of ligands around the chiral iridium center. The metals are η5-bonded to the pentamethylcyclopentadienyl group, linked in a chelate fashion through the aminic nitrogen and one of the carboxylate oxygens to the amino acidate, and bonded to a terminal almost linear tert-butyl ethynyl ligand. The configurational stability of the complexes was studied by circular dichroism and 1H NMR spectroscopy. Complex 3b epimerizes at Ir in CDCl3 obeying a first-order rate law with ΔH = 91.4 ± 3.4 kJ mol-1 and ΔS-= −20.8 ± 10.8 J K-1 mol-1. The equilibrium constant for 3b 3a is 2.70 ± 0.41 in methanol at 20 °C. A mechanistic interpretation of the epimerization process is proposed.
A method is presented to determine the absolute hydration enthalpy of the proton, ΔHaq°[H+], from a set of cluster-ion solvation data without the use of extra thermodynamic assumptions. The absolute proton hydration enthalpy has been found to be 50 kJ/mol different than traditional values and has been more precisely determined (by about an order of magnitude). Conventional ion solvation properties, based on the standard heat of formation of H+(aq) set to zero, have been devised that may be confusing to the uninitiated but are useful in thermochemical evaluations because they avoid the unnecessary introduction of the larger uncertainties in our knowledge of absolute values. In a similar strategy, we have motivated the need for a reassessment of ΔHaq°[H+] by the trends with increased clustering in conventional cluster-ion solvation enthalpy differences for pairs of oppositely charged cluster ions. The consequences of particular preferred values for ΔHaq°[H+] may be evaluated with regard to cluster-ion properties and how they connect to the bulk. While this approach defines the problem and is strongly suggestive of the currently determined proton value, it requires extra thermodynamic assumptions for a definitive determination. Instead, a unique reassessment has been accomplished without extra thermodynamic assumptions, based on the known fraction of bulk absolute solvation enthalpies obtained by pairs of oppositely charged cluster ions at particular cluster sizes. This approach, called the cluster-pair-based approximation for ΔHaq°[H+], becomes exact for the idealized pair of ions that have obtained the same fraction of their bulk values at the same cluster size. The true value of ΔHaq°[H+] is revealed by the linear deviations of real pairs of ions from this idealized behavior. Since the approximation becomes exact for a specific pair of oppositely charged ions, the true value of ΔHaq°[H+] is expected to be commonly shared on plots of the approximation vs the difference in cluster-ion solvation enthalpy for pairs of ions sharing the same number of solvating waters. The common points on such plots determine values of −1150.1 ± 0.9 kJ/mol (esd) for ΔHaq°[H+] and −1104.5 ± 0.3 kJ/mol (esd) for ΔGaq°[H+]. The uncertainties (representing only the random errors of the procedure) are smaller than expected because the cluster data of 20 different pairings of oppositely charged ions are folded into the determination.
The reductive formation of substituted anilines from amines and three well-defined aryl- gold(III) complexes, i.e., dichloro(2,6-lutidine)phen- ylgold(III) (2), dichloro(2,6-lutidine)-p-tolylgold(III) (3), and chlorobis(triphenylphosphine)phenylgold(III) chloride (4) was studied. The reaction is stoichiometric in gold and represents a key step of a potential gold-catalyzed intermolecular amination reaction of arenes. It proceeds smoothly with a broad range of N-nucleophiles in the presence of sodium acetate (NaOAc) and enables the selective formation of N-substituted anilines in good yields. A mechanistic pathway is proposed and discussed as well.
Di-μ-Chloro-dichlorobis(η5-pentamethylcyclopentadienyl)dirhodium(III),[RhCp*Cl2]2 Di-μ-Chloro-dichlorobis(η5-pentamethylcyclopetandienyl)diiridium(III),[IrCp*Cl2]2 Tris(acetonitrile)(η5-pentamethylcyclopentadienyl)rhodium(2+)Hexafluorophosphate,[RhCp*(NCMe)3][PF6]2 Tris(acetonitrile)(η5-pentamethyulcyclopentadienyl)iridium(2+)Hexafluorophosphate, [IrCp*(NCMe)3][PF6]2 Preparation of Tris(η5-pentamethylcyclopentadienyl)iridium(2+)and Its Reacation with Fluorene Give (η5-Fluorene)(η5-pentamethylcyclopentadienyl)iridiuim(2+),[IrCp*(C13H10)][PF6]2
Durch Umsetzung von chloroverbrückten Verbindungen mit Sarkosinat, N-Methylalaninat und Ethylendiamin-N, N′-diacetat wurden die Halbsandwich-Chelat-Komplexe [Cp*M(Cl)(NHMeCHRCO2)] (M = Ir, Rh; R = H, Me), [(p-Cymol)Ru(Cl)(NHMeCHRCO2)] (R = H, Me) mit chiralen Metall- und N-Atomen, die Palladium- und Platin-Komplexe [(R3P)(Cl)M(NHMeCHR′CO2)] (M = Pd, Pt; R′ = H, Me) sowie die zweikernigen Komplexe [(Cl)(R3P)M(O2CCH2NHCH2CH2NHCH2CO2)M(PR3)(Cl)] erhalten. Die bei diesen Komplexen möglichen Diastereomeren werden anhand der 1H-, 13C- und 31P-NMR-Daten diskutiert.M-Metal Complexes with Biological Important Ligands. CLIV [1] Halfsandwich Complexes of Rhodium, Iridium, Ruthenium and Phosphine containing Palladium and Platinum Complexes with Sarcosinate, N-Methylalaninate, and Ethylenediamine-N, N′-diacetateReactions of chloro bridged complexes with sarcosinate, N-methylalaninate and ethylenediamine-N, N′-diacetate give the halfsandwich complexes [Cp*M(Cl)(NHMeCHRCO2)] (M = Ir, Rh; R = H, Me), [(p-cymene)Ru(Cl)(NHMeCHRCO2)] (R = H, Me) with chiral metal and N-atoms, the palladium and platinum complexes [(R3P)(Cl)M(NHMeCHR′CO2)] (M = Pd, Pt; R′ = H, Me) and the dinuclear compounds [(Cl)(R3P)M(O2CCH2NHCH2CH2NHCH2CO2)M(PR3)(Cl)]. The possible diastereoisomers of these complexes are discussed on the basis of their 1H, 13C, and 31P NMR spectra.
The formation of [{(η-ring)M(Aa)}3](BF4)3trimers [(η-ring)M=(η5-C5Me5)Rh, (η5-C5Me5)Ir, (η6-p-MeC6H4iPr)Ru; Aa = α-amino acidate, one cation shown schematically] takes place by chiral self-recognition, the RMRMRM or SMSMSM trimers are equally configurated at the metal centres and are the only diastereomers detected. The equilibrium constant for the diastereomerisation process between both isomers depends on the solvent, amino acidate, and metal. The trimers catalyse the reduction of unsaturated aldehydes to unsaturated alcohols and the reduction of acetophenone to 2-phenylethanol with up to 75 % ee.
Several aliphatic alcohols including those bearing functional groups are transformed to the corresponding amines by reaction with primary or secondary amines in the presence of catalyst IPA.
The perchlorate complexes of a series of half-sandwich monoaqua cations Cp*Ir(A−B)(H2O)2+/+ with A−B = prol (D/L-proline anion), picac (picolinic acid anion), R,R-dach [(−)-(1R,2R)-1,2-diaminocyclohexane], R,R-dpen [(+)-(1R,2R)-1,2-diphenylethylenediamine], phen (o-phenanthroline), and bpy (2,2′-bipyridine) (Cp* = η5-pentamethylcyclopentadienyl anion) have been prepared and characterized. An X-ray structure analysis of Cp*Ir(R,R-dach)(H2O)(ClO4)2·H2O has revealed that the cation Cp*Ir(R,R-dach)(H2O)2+ has a distorted pseudo-octahedral coordination geometry. In the case of A−B = prol, crystallization from water led to the trinuclear complex [Cp*Ir(D-prol)]3(ClO4)3, which has also been characterized by X-ray structure analysis. The experimental data suggest that in aqueous solution the trinuclear proline complex dissociates to form the cation Cp*Ir(D-prol)(H2O)+. The proton dissociation constants of the coordinated water in Cp*Ir(A−B)(H2O)2+/+ have been determined as pKa = 7.5 (A−B = bpy) and pKa = 7.1 (A−B = R,R-dach and picac). Substitution of the water in Cp*Ir(A−B)(H2O)2+/+ by the monodentate ligands L = py (pyridine), DMS (dimethyl sulfide), TU (thiourea), and monodentate anions according to the Equation Cp*Ir(A−B)(H2O)2+/+ + L → Cp*Ir(A−B)L2+/+ + H2O has been studied by multi-wavelength stopped-flow spectrophotometry in aqueous solution at I = 0.2 M. This kinetic investigation, carried out at different concentrations, temperatures, and pressures, showed that the process obeys second-order kinetics, where rate = kL[Cp*Ir(A−B)H2O2+/+][L]. The magnitude of the second-order rate constant kL depends on the nature of both A−B and L. The data for kL have been found to range from 6.4 × 104M−1s−1 (A−B = D-prol; L = TU) to 10.5 M−1s−1 (A−B = bpy; L = py) at 298 K. The activation parameters for water substitution at Cp*Ir(A−B)(H2O)2+/+ (A−B = bpy, R,R-dach, and picac) by L = TU have been evaluated. The activation volumes of ΔV≠ = +2.3, +7.4, and +7.3 cm3 mol−1, respectively, are supportive of an Id mechanism. The results regarding the kinetic lability of the coordinated water in the monoaqua cations Cp*Ir(A−B)(H2O)2+/+ are compared to those obtained for the triaqua cation Cp*Ir(H2O)32+.
An efficient and environmentally benign catalytic system for the synthesis of various organic amines catalyzed by the water-soluble and air-stable (pentamethylcyclopentadienyl)-iridium-ammine iodide complex, [Cp*Ir(NH(3))(3)][I](2) (Cp* - pentamethylcyclopentadienyl), has been developed. A wide variety of secondary and tertiary amines were synthesized by the N-alkylation reactions of theoretical equivalents of amines with alcohols in water under air without a base. The synthesis of cyclic amines was also achieved by the N-alkylation of benzylamine with diols. Furthermore, the recycle use of the present water-soluble Cp*Ir catalyst was accomplished.
Introduction: Purposes of This ChapterDerivation of Tabulated DataTabulations
A versatile and highly atom economical catalytic system consisting of [Cp*IrCl 2 ] 2 /NaHCO 3 (Cp*¼pentamethylcyclopentadienyl) for the N-alkylation of amines with primary and secondary alcohols as alkylating reagents has been developed. For example, the reaction of equimolar amounts of aniline and benzyl alcohol in the presence of [Cp*IrCl 2 ] 2 (1.0 mol % Ir) and NaHCO 3 (1.0 mol %) in toluene at 110 C gives N-benzylaniline in 94% yield. The present catalytic system is applicable to the N-alkylation of both primary and secondary amines, and only harmless water is produced as co-product. A wide variety of secondary and tertiary amines can be synthesized with high atom economy under mild and less-toxic conditions. One-pot sequential N-alkylation leading to tertiary amines bearing three different substituents is also described.
A comparative study on the catalytic activity of a series of [IrCl(2)Cp*(NHC)] complexes in several C-O and C-N coupling processes implying hydrogen-borrowing mechanisms has been performed. The compound [IrCl(2)Cp*(I(nBu))] (Cp*=pentamethyl cyclopentadiene; I(nBu)=1,3-di-n-butylimidazolylidene) showed to be highly effective in the cross-coupling reactions of amines and alcohols, providing high yields in the production of unsymmetrical ethers and N-alkylated amines. A remarkable feature is that the processes were carried out in the absence of base, phosphine, or any other external additive. A comparative study with other known catalysts, such as Shvo's catalyst, is also reported.
The hydroamination of alkenes represents an atom-economical strategy for the synthesis of nitrogen-containing molecules from readily available components. In recent years, the application of Group 9 transition metal catalysts in this reaction has enabled significant progress to be made toward addressing several major challenges within the field of metal-mediated hydroamination. Using Rh- and Ir-based catalysts for the intermolecular hydroamination reaction, advances have been made in the regioselective addition of amines to olefins in an anti-Markovnikov fashion producing industrially relevant linear amine products, as well as the concise synthesis of chiral amines by asymmetric hydroamination. The intramolecular addition of a variety of amine groups to pendant alkenes has also been studied in the context of developing expedient routes to nitrogen-containing heterocycles; using simple Rh- and Ir-based catalysts, a wide range of substrates including those that contain functional groups that are poised for further synthetic elaboration are readily cyclized. Extension of these catalyst systems to include the asymmetric synthesis of a variety of functionalized 1-methylpyrrolidine compounds has recently been achieved. To complement these catalytic investigations, thorough stoichiometric and kinetic studies have unveiled diverse mechanistic pathways that originate from either initial amine or olefin activation. The understanding gained through these mechanistic investigations provides the framework for the design of increasingly effective alkene hydroamination catalysts.
We present auxilliary basis sets for the atoms H to At – excluding the Lanthanides – optimized for an efficient treatment
of molecular electronic Coulomb interactions. For atoms beyond Kr our approach is based on effective core potentials to describe
core electrons. The approximate representation of the electron density in terms of the auxilliary basis has virtually no effect
on computed structures and affects the energy by less than 10−4 a.u. per atom. Efficiency is demonstrated in applications for molecules with up to 300 atoms and 2500 basis functions.
Contracted Gaussian basis sets of triple zeta valence (TZV) quality are presented for Li to Kr. The TZV bases are characterized by typically including a single contraction to describe inner shells and three basis functions for valence shells. All parameters—orbital exponents and contraction coefficients—have been determined by minimization of atomic self-consistent field ground state energies. Advantages and necessary modifications of TZV basis sets are discussed for simple test calculations of molecular energies and nuclear magnetic resonance (NMR) chemical shieldings in treatments with and without inclusion of electron correlation. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.
A role for electronic structure databases in assisting users of quantum chemistry applications select better model parameters is discussed in light of experiences gained from a software prototype known as the Computational Chemistry Input Assistant (CCIA). It is argued that the ready availability of information pertaining to the applications and theoretical models can substantially increase the likelihood of novice users obtaining the desired accuracy from their calculations while simultaneously making better use of computer resources. Expert users, who find themselves contemplating studies in new areas of research, may also benefit from the proposed tools. For maximum impact, this assistance should be provided while users are actively engaged in preparing calculations. © 1996 by John Wiley & Sons, Inc.
Cationic platinum(II) complexes with bi- or tridentate (pincer) functionalized NHC ligands were found to be catalytically active in the hydroamination of unactivated alkenes. In some cases, the presence of water had an activating effect on the complexes. Reactions with the N-nucleophilic substrate morpholine led to a noncatalytic reaction in which the deprotonation product of the key cationic beta-aminoalkyl platinum complex could be isolated and characterized. Surprisingly, attempted protonation of this complex did not give the expected N-alkylated product, indicating either the thermodynamic unfavorability of C-Pt bond cleavage or its kinetic inertness.
Despite the remarkable thermochemical accuracy of Kohn–Sham density-functional theories with gradient corrections for exchange-correlation [see, for example, A. D. Becke, J. Chem. Phys. 96, 2155 (1992)], we believe that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional containing local-spin-density, gradient, and exact-exchange terms is tested on 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total atomic energies of first- and second-row systems. This functional performs significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.
Basis sets are some of the most important input data for computational models in the chemistry, materials, biology, and other science domains that utilize computational quantum mechanics methods. Providing a shared, Web-accessible environment where researchers can not only download basis sets in their required format but browse the data, contribute new basis sets, and ultimately curate and manage the data as a community will facilitate growth of this resource and encourage sharing both data and knowledge. We describe the Basis Set Exchange (BSE), a Web portal that provides advanced browsing and download capabilities, facilities for contributing basis set data, and an environment that incorporates tools to foster development and interaction of communities. The BSE leverages and enables continued development of the basis set library originally assembled at the Environmental Molecular Sciences Laboratory.
The reaction of primary and secondary amines with benzylic alcohols (II) under thermal conditions provides a synthesis of higher amines.