Rhodium(I)–(N-heterocyclic carbene)–diphosphine complexes

Abstract

Reactions of [RhCl(COE)(IPr)]2 (1) and [RhCl(COE)(IMes)]2 (2) (COE = cyclooctene; IPr = N,N′-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; IMes = N,N′-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) with the diphosphines Ph2P(CH2)nPPh2 and 1,2-bis(diphenylphosphino)benzene (dppbz) give the N-heterocyclic carbene (NHC) – diphosphine – rhodium(I) complexes: RhCl(NHC)[Ph2P(CH2)nPPh2] [NHC = IPr, n = 1 (3); NHC = IMes, n = 1 (4); NHC = IPr, n = 2 (5); NHC = IMes, n = 2 (6); NHC = IPr, n = 4 (7); NHC = IMes, n = 4 (8)] and RhCl(NHC)(dppbz) [NHC = IPr (9); NHC = IMes (10)]. All the complexes are characterized by 1H, 31P{1H}, and 13C{1H} NMR spectroscopy, elemental analysis, and mass spectrometry. Complexes 3, 7, and 9 are also characterized crystallographically. In benzene solution, the complexes decompose in the presence of O2 with formation of the diphosphine dioxide, whereas reaction with CO leads to replacement of the NHC ligand to give known carbonyl–diphosphine complexes.