Rhodium Carbene Complexes: Highly Selective Catalysts for the Hydroformylation of Styrene Derivatives
作者:Austin C. Chen、Li Ren、Andreas Decken、Cathleen M. Crudden
DOI:10.1021/om0003739
日期:2000.9.1
Two new carbene−rhodium complexes are reported that are active hydroformylation catalysts, giving very high selectivities for the branched isomer (>95:5) when vinyl arenes are used as substrates. The carbene analogue of Wilkinson's catalyst, [RhIMes(PPh3)2Cl] (IMes = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene), and the related carbonyl complex [RhIMes(PPh3)(CO)Cl] were both prepared, and the
Structural characterization and catalytic activity of the rhodium–carbene complex Rh(PPh3)2(IMes)Cl (IMes=bis(1,3-(2,4,6-trimethylphenyl)imidazol-2-ylidene)
作者:Gabriela A. Grasa、Zakhia Moore、Kenneth L. Martin、Edwin D. Stevens、Steven P. Nolan、Valérie Paquet、Hélène Lebel
DOI:10.1016/s0022-328x(02)01638-8
日期:2002.9
The rhodium-carbene complex Rh(PPh3)(2)(IMes)Cl (2) is an active catalyst for the hydroboration of simple olefins at room temperature. The reactivity of 2 was also tested in the methylenation of aldehydes. The crystal structure of 2 is also reported (C) 2002 Elsevier Science B.V. All rights reserved.
Irreversible cleavage of a carbene–rhodium bond in Rh-N-heterocyclic carbene complexes: implications for catalysis
作者:Daryl P. Allen、Cathleen M. Crudden、Larry A. Calhoun、Ruiyao Wang
DOI:10.1016/j.jorganchem.2004.07.021
日期:2004.9
Despite the generally accepted belief that carbene-metal bonds are strong and do not dissociate, the reaction of Rh-N-heterocyclic carbene complexes with triphenylphosphine in dichloroethane was determined to take place via cleavage of the Rh-carbene bond. The products of this reaction are Wilkinson's catalyst and a bisimiclazolium salt derived from reaction between dichloroethane and two equivalents of the carbene. The implications of this reaction for catalysis are significant since the carbene complex shows lower activity than Wilkinson's catalyst in hydrogenation reactions. In non-halogenated solvents, the catalyst shows higher stability, such that the rate of exchange with free phosphine could be measured, and was determined to be ca. 10 times slower than in Wilkinson's catalyst. (C) 2004 Elsevier B.V. All rights reserved.