Catalytic Activity In Transfer Hydrogenation Research Articles

Dicarbonylruthenium(II) complexes of diphosphine ligands and their catalytic activity

Abstract The hexa-coordinated chelate complexes of the type [Ru(CO)2Cl2(P-P)](1a,b) [where P-P = 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene(a) and [bis(2-diphenylphosphinophenyl)ether(b)] have been synthesized by reacting the polymeric precursor [Ru(CO)2Cl2]n with the ligands in 1:1 molar ratio. The complexes 1a,b are characterized by elemental analyses, Mass, IR and NMR spectroscopy together with the single crystal X-ray structure determination of 1a. The compound 1a crystallizes in a monoclinic system with space group C2/c showing a slightly distorted octahedral geometry around the Ru centre. The complexes 1a and 1b are thermally stable up to 300 °C and exhibit high catalytic activity in transfer hydrogenation of aldehyde and ketones to corresponding alcohols. The complexes 1a and 1b show much higher catalytic activity for the hydrogenation of aldehyde than ketones. In general, the catalytic efficiency of 1b is higher compared with 1a.

Diastereomeric half-sandwich Ru(II) cationic complexes containing amino amide ligands. Synthesis, solution properties, crystal structure and catalytic activity in transfer hydrogenation of acetophenone

The cationic complexes [( η 6-arene)Ru(N,O-amino amide)X]Y (arene = p-cymene or indane; N,O-amino amide = ( l)-proline amide or ( l)-phenylalanine amide; X = Cl or I; Y = Cl, I or PF 6) have been synthesised and fully characterized by spectroscopic and analytical methods. In several cases ( 1a, 3a, 4a, 4b, 5) the metal configuration has been definitively established by X-ray analysis on single crystal. The lability of the metal center in solution has been studied by 1H NMR and CD techniques. The highest configurational stability has been found in the complexes of the type [( η 6-indane)Ru(N,O-proline amide)Cl]Y ( 4a,b). The complexes 1b, 2a–b, 3b, 4b and 5 are good precatalysts for the transfer hydrogenation of acetophenone in basic i-PrOH, with ee up to 76% at 30 °C. An ESI(+)-MS study of pre-catalytic solutions has provided useful information on the catalytic mechanism.

Quinoline-functionalized N-heterocyclic carbene complexes of iridium: Synthesis, structures and catalytic activities in transfer hydrogenation

Abstract Iridium complexes containing quinoline-functionalized N-heterocyclic carbene (NHC) ligands have been synthesized by the transmetalation route from silver carbene precursors. The silver complexes undergo a facile reaction with [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) to yield a series of carbene complexes [(NHC)Ir(COD)Cl] (NHC = 3-methyl-1-(8-quinolylmethyl)imidazole-2-ylidene (2a); 3-n-butyl-1-(8-quinolylmethyl)imidazole-2-ylidene (2b); 3-benzyl-1-(8-quinolylmethyl)imidazole-2-ylidene (2c); 1,3-di(8-quinolylmethyl)imidazole-2-ylidene (2d). The coordinated COD was replaced by carbon monoxide to yield the corresponding carbonyl species [(NHC)Ir(CO)2Cl] (3). Complexes 2 and 3 have been characterized by IR, ESI-MS, 1H and 13C NMR and elemental analyses. The molecular structures of complexes 2b and 2c have been confirmed by single-crystal X-ray diffraction. Two analogous Ir(I) complexes 5 and 6 with naphthalene-containing NHC have also been synthesized and characterized. These Ir(I) complexes in the current work have been proved to be active catalysts in the transfer hydrogenation of ketones to alcohols using 2-propanol as the hydrogen source.

Syntheses, Structures, and Catalytic Properties of Ruthenium(II) Nitrosyl Complexes with Pyridine-Functionalized N-Heterocyclic Carbenes

Ruthenium(II) nitrosyl complexes with pyridine-functionalized N-heterocyclic carbenes [(L)Ru(NO)Cl3] [L = 3-tert-butyl-1-(2-pyridyl)imidazol-2-ylidene, 2a; 3-n-butyl-1-(2-pyridyl)imidazol-2-ylidene, 2b; 3-tert-butyl-1-picolylimidazol-2-ylidene, 2c; 3-n-butyl-1-picolylimidazol-2-ylidene, 2d; and 3-benzyl-1-picolylimidazol-2-ylidene, 2e] have been prepared by transmetalation from the corresponding silver carbene complexes. Compounds 2a−c have been characterized by single-crystal X-ray crystallography. Compounds 2a−e show catalytic activities in transfer hydrogenation of ketones.

N-heterocyclic carbenes of iridium(I): ligand effects on the catalytic activity in transfer hydrogenation

New Ir-NHC complexes based on different heterocyclic moieties like imidazole, benzimidazole and imidazolidine are presented and tested in transfer hydrogenation catalysis. A broad range of steric and electronic properties of NHC ligands is covered to give an idea for catalyst design from the experimental point of view.

Pyridine-Based N-Heterocyclic Carbene Hydride Complexes of Iridium via C−H Activation

A series of iridium(III) hydride complexes of chelating pyridine-based N-heterocyclic carbenes (py-NHCs) and remote N-heterocyclic carbenes (remote py-NHCs) were synthesized as stable products from the C-H oxidative addition reactions of pyridine-tethered pyridinium halides and [Ir(COD)(2)](+). X-ray crystal structures of representative iridium py-NHC and remote py-NHC complexes were determined and in all cases mutual cis orientations of the halide and hydride ligands were observed in the solid state. In the solution phase, the cis isomer was observed as the only product for each iridium(III) py-NHC complex, whereas both cis and trans isomers have been observed as equilibration mixtures for iridium(III) remote py-NHC complexes. No beta-insertion of the hydride into a C=C bond of the COD unit of iridium(III) py-NHC hydride complexes was observed, and theoretical studies indicate that this step is thermodynamically unfavorable. Iridium(III) py-NHC hydride complexes have shown high catalytic activity in transfer hydrogenation of ketone and enones. Computational studies of the donor capacity of those ligands indicate that py-NHCs are more donating than imidazole-derived NHCs.

Rhodium(III) Complexes Containing C4-Bound N-Heterocyclic Carbenes: Synthesis, Coordination Chemistry, and Catalytic Activity in Transfer Hydrogenation

Direct metalation of C2-protected diimidozolium salts with RhCl3 or [RhCl(cod)]2 and KI afforded a series of new rhodium(III) complexes with abnormally C4-bound, cis-chelating NHC ligands. The complexes were isolated as dimetallic species containing two (μ2-I)3-bridged rhodium(III) centers. In the presence of coordinating ligands such as CH3CN, PPh3, or dppe, the dimeric structure is readily cleaved and yields monometallic complexes. Crystallographic analysis of representative structures indicates a higher trans influence of abnormally C4-bound carbenes as compared to normal NHCs. The exceptionally strong donor ability of carbenes in such a C4 coordination mode increases the catalytic activity of the rhodium center and allows for efficient transfer hydrogenation of ketones in iPrOH/KOH.

Hemilabile Pincer-Type Hydride Complexes of Iridium

The ligand tBu2PC2H4NHC2H4NEt2 (PNHN) was synthesized starting from 2-(diethylamino)ethyl chloride hydrochloride and ethanolamine. Reaction of PNHN with [IrCl(COE)2]2 under H2 afforded the dihydride cis-IrH2Cl(κ3-PNHN) (1) in excellent yield. Treatment of 1 with tBuOK led to clean formation of the 16-electron amido complex IrH2(κ3-PNN) (2). Hydrogenation of 2 in toluene or ethyl acetate produced the trihydride mer-IrH3(κ3-PNHN) (3). This complex was unstable and dimerized to give [IrH2(κ2-PNHN)]2(μ-H)2 (4) with uncoordinated NEt2 groups. The structures of 1 and 4 were established by X-ray crystallography. Complex 2 demonstrated good catalytic activity for transfer hydrogenation of acetophenone, cyclohexanone, and butanone.

Relating catalytic activity and electrochemical properties: The case of arene–ruthenium phenanthroline complexes catalytically active in transfer hydrogenation

The electrochemical properties of cationic complexes [(η 6-arene)Ru(N ∩ N)Cl]Cl (arene/N ∩ N = C 6H 6/1,10-phenanthroline ( 1), p-MeC 6H 4Pr i /1,10-phenanthroline ( 2), C 6Me 6/1,10-phenanthroline ( 3), C 6Me 6/5-NO 2-1,10-phenanthroline ( 4), and C 6Me 6/5-NH 2-1,10-phenanthroline ( 5)) were studied by cyclic voltammetry in order to rationalize catalytic activity in transfer hydrogenation of the respective aqua complexes [(η 6-arene)Ru(N ∩ N)(OH 2)](BF 4) 2 ( 6– 10). Complexes 1– 5 were chosen because the ‘true’ catalysts 6– 10 are unstable under the conditions of the measurement. The electrochemical behaviour of 1– 5 in acetonitrile solution is rather complicated due to consecutive and parallel chemical reactions that accompany electron transfer processes. Nonetheless, interpretation of the electrochemical data allowed to assess the influence of the structure and substitution on the redox and catalytic properties: the catalytic ability correlates with the reduction potentials, indicating the decisive role of the η 6-arene ring directly bonded to the catalytic centre (Ru).

Ruthenium(II) complexes containing 2-diphenylphosphinobenzaldehyde: synthesis and catalytic activity in transfer hydrogenation §

The reaction of dimers [Ru(η 6-arene)(μ-Cl)Cl] 2 (arene=C 6H 6 ( 2a); 1- iPr-4-C 6H 4Me ( 2b); 1,2,4,5-C 6H 2Me 4 ( 2c); C 6Me 6 ( 2d)) with 2-diphenylphosphinobenzaldehyde ( 1) yields the neutral complexes [Ru(η 6-arene)Cl 2(κ 1- P-2-Ph 2PC 6H 4CHO)] ( 3a– d). Treatment of compounds 3a– d with one equivalent of AgSbF 6 leads to the formation of the monocationic derivatives [Ru(η 6-arene)Cl(κ 2- P, O-2-Ph 2PC 6H 4CHO)][SbF 6] ( 4a– d). When 3a– d are treated with two equivalents of AgSbF 6 in presence of acetone, the dicationic complexes [Ru(η 6-arene)(κ 1- O-Me 2CO)(κ 2- P, O-2-Ph 2PC 6H 4CHO)][SbF 6] 2 (arene=C 6H 6 ( 5a); 1- iPr-4-C 6H 4Me ( 5b); 1,2,4,5-C 6H 2Me 4 ( 5c); C 6Me 6 ( 5d)) are obtained. Complexes 3– 5a– d have proven to be active catalysts in transfer hydrogenation of acetophenone by propan-2-ol.

Synthesis, reactivity and catalytic activity in transfer hydrogenation of ketones of ruthenium(ii) and ruthenium(iv) complexes containing the novel N-thiophosphorylated iminophosphorane-phosphine ligands Ph2PCH2P{NP(S)(OR)2}Ph2(R = Et, Ph)

Download options Please wait... Supplementary files Analytical and spectroscopic data PDF (190K) Crystal structure data TXT (40K) Article information DOI https://doi.org/10.1039/B305520E Article type Paper Submitted 16 May 2003 Accepted 25 Jun 2003 First published 14 Jul 2003 Download Citation Dalton Trans., 2003, 3240-3249 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Synthesis, reactivity and catalytic activity in transfer hydrogenation of ketones of ruthenium(II) and ruthenium(IV) complexes containing the novel N-thiophosphorylated iminophosphorane-phosphine ligands Ph2PCH2P{NP(S)(OR)2}Ph2 (R = Et, Ph) V. Cadierno, P. Crochet, J. Díez, J. García-Álvarez, S. E. García-Garrido, S. García-Granda, J. Gimeno and M. A. Rodríguez*, Dalton Trans., 2003, 3240 DOI: 10.1039/B305520E To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Victorio Cadierno Pascale Crochet Josefina Díez Joaquín García-Álvarez Sergio E. García-Garrido Santiago García-Granda José Gimeno Miguel A. Rodríguez*

Stable N-functionalised ‘pincer’ bis carbene ligands and their ruthenium complexes; synthesis and catalytic studies

Deprotonation of 2,6-bis(arylimidazolium)pyridine dibromide with KN(SiMe3)2 gave thermally stable 2,6-bis(arylimidazol-2-ylidene)pyridine, which was further used to prepare ruthenium ‘pincer’ complexes; the latter show catalytic activity in transfer hydrogenation of carbonyl compounds.

ChemInform Abstract: Five‐ and Six‐Coordinate Ruthenium(II) Complexes Containing 2‐Ph2PC6H4CH=NtBu and 2‐Ph2PC6H4CH2NHtBu as Chelate Ligands: Synthesis, Characterization, and Catalytic Activity in Transfer Hydrogenation of Ketones.

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