Triarylphosphine, hydride, and ethylene complexes or rhodium(I) chloride

Tolman, Chadwick A.; Meakin, Paul; Lindner, D. I.; Jesson, J. P.

doi:10.1021/ja00816a018

Cited by 256 publications

(97 citation statements)

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“…This surprising observation is explained by the generation of catalytically less active dimeric rhodium species in solution under hydrogen pressure. [142] In an interphase, however, this dimerization process is prevented or at least impeded, as the monomeric rhodium(i) complex centers are spatially isolated in the stationary phase…”

Section: Hydrogenationmentioning

confidence: 99%

Chemistry in Interphases—A New Approach to Organometallic Syntheses and Catalysis

Lindner

Schneller

Auer

et al. 1999

Angew. Chem. Int. Ed.

229

115

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Combining the advantages of homogeneous and heterogeneous catalysis is still a problem that has not been satisfactorily solved. Chemistry in interphases offers a new approach for overcoming the difficulties, as is described in this article. Owing to the swellable or porous matrix, an interphase represents a state which in the most favorable case is similar to that of a solution. Moreover the proper choice of a mobile hybrid copolymer enables the control of the density and accessibility of the reactive centers, which results in a distinct improvement of the activity of the catalysts (two examples are shown schematically).

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Section: Hydrogenationmentioning

confidence: 99%

Chemistry in Interphases—A New Approach to Organometallic Syntheses and Catalysis

Lindner

Schneller

Auer

et al. 1999

Angew. Chem. Int. Ed.

229

115

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“…Magnetisation transfer from the hydride ligands of these complexes into the alkyl group of the hydrogenation product is also observed. 3 ] are observed in addition to the corresponding binuclear alkene±dihydride products. The higher initial activity of these precursors is offset by the formation of the trirhodium phosphide bridged deactivation product, [{(H)(PPh 3 )Rh(m-H)(m-I)(matures and pressures, [2,3] and although the slow reduction of unsaturated alkenes by H 2 in the presence of metal ions such as Ag + or Cu 2 + was already known, [4] [RhCl(PPh 3 3 ] is capable of promoting selective hydrogenation of C=C or CC groups in the presence of other easily reducible functionalities such NO 2 or CHO.…”

Section: Introductionmentioning

confidence: 99%

Hydrogenation Studies Involving Halobis(phosphine)–Rhodium(i) Dimers: Use of Parahydrogen Induced Polarisation To Detect Species Present at Low Concentration

Colebrooke

Duckett

Lohman

et al. 2004

Chemistry A European J

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Reaction of [RhCl(PPh3)2]2 with parahydrogen revealed that the binuclear dihydride [Rh(H)2(PPh3)2mu-Cl)2Rh(PPh3)2] and the tetrahydride complex [Rh(H)2(PPh3)2(mu-Cl)]2 are readily formed. While magnetisation transfer from free H2 into both the hydride resonances of the tetrahydride and [Rh(H)2Cl(PPh3)3] is observable, neither transfer into [Rh(H)2(PPh3)2(mu-Cl)2Rh(PPh3)2] nor transfer between the two binuclear complexes is seen. Consequently [Rh(H)2(PPh3)2(mu-Cl)]2 and [Rh(H)2(PPh3)2(mu-Cl)2Rh(PPh3)2] are not connected on the NMR timescale by simple elimination or addition of H2. The rapid exchange of free H2 into the tetrahydride proceeds via reversible halide bridge rupture and the formation of [Rh(H)2(PPh3)2(mu-Cl)RhCl(H)2(PPh3)2]. When these reactions are examined in CD2Cl2, the formation of the solvent complex [Rh(H)2(PPh3)2(mu-Cl)2Rh(CD2Cl2)(PPh3)] and the deactivation products [Rh(Cl)(H)PPh3)2(mu-Cl)(mu-H)Rh(Cl)(H)PPh3)2] and [Rh(Cl)(H)(CD2Cl2)(PPh3)(mu-Cl)(mu-H)Rh(Cl)(H)PPh3)2] is indicated. In the presence of an alkene and parahydrogen, signals corresponding to binuclear complexes of the type [Rh(H)2(PPh3)2(mu-Cl)(2)(Rh)(PPh3)(alkene)] are detected. These complexes undergo intramolecular hydride interchange in a process that is independent of the concentration of styrene and catalyst and involves halide bridge rupture, followed by rotation about the remaining Rh-Cl bridge, and bridge re-establishment. This process is facilitated by electron rich alkenes. Magnetisation transfer from the hydride ligands of these complexes into the alkyl group of the hydrogenation product is also observed. Hydrogenation is proposed to proceed via binuclear complex fragmentation and trapping of the resultant intermediate [RhCl(H)2PPh3)2] by the alkene. Studies on a number of other binuclear dihydride complexes including [(H)(Cl)Rh(PMe3)2(mu-H)(mu-Cl)Rh(CO)(PMe3)], [(H)2Rh(PMe3)2(mu-Cl)2Rh(CO)(PMe3)] and [HRh(PMe3)2(mu-H)(mu-Cl)2Rh(CO)(PMe3)] reveal that such species are able to play a similar role in hydrogenation catalysis. When the analogous iodide complexes [RhIPPh3)2]2 and [RhI(PPh3)3] are examined, [Rh(H)2(PPh3)2(mu-I)2Rh(PPh3)2], [Rh(H)2(PPh3)2(mu-I)]2 and [Rh(H)2I(PPh3)3] are observed in addition to the corresponding binuclear alkene-dihydride products. The higher initial activity of these precursors is offset by the formation of the trirhodium phosphide bridged deactivation product, [[(H)(PPh3)Rh(mu-H)(mu-I)(mu-PPh2)Rh(H)(PPh3)](mu-I)2Rh(H)2PPh3)2]

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“…1 show that the "P,RhClW polymers B(n,m) are generally considerably more active than their "P4Rh,C1," analogues C(n,m). In homogeneous solution the catalytic activity of [(C,H,),P],RhCl appears to be The dimer itself is described as a good hydrogenation catalyst (19) but with little substantiation. We have shown that model complexes for the silicone polymers B, C, and D, L3RhCl and L4Rh,Cl, (20) (L = [(CH3)3SiO],Si(CH3)CH2CHzP(C6H5)2) are both active catalysts for styrene hydrogenation with the dimer being less active.…”

Section: )mentioning

confidence: 99%

Polymeric siloxyphosphine rhodium(I) complexes as hydrogenation catalysts

Brzezińska¹,

Cullen²,

Strukul³

1980

Can. J. Chem.

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Triarylphosphine, hydride, and ethylene complexes or rhodium(I) chloride

Abstract: Physical studies, combining molecular weights, 31P, 13C, and 'H nmr, infrared, and spectrophotometric measurements, have been made to define the species and rates and equilibria of reactions in solutions con-

Cited by 256 publications

References 0 publications

Chemistry in Interphases—A New Approach to Organometallic Syntheses and Catalysis

Chemistry in Interphases—A New Approach to Organometallic Syntheses and Catalysis

Hydrogenation Studies Involving Halobis(phosphine)–Rhodium(i) Dimers: Use of Parahydrogen Induced Polarisation To Detect Species Present at Low Concentration

Polymeric siloxyphosphine rhodium(I) complexes as hydrogenation catalysts

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