Rhodium(I) - (N-heterocyclic carbene) - Diphosphine complexes

Article abstract of DOI:10.1139/V09-118

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-trmiethylphenyl)miidazomi-2-ylidene) with the diphosphines Ph₂P(CH₂)_nPPh ₂ and 1,2-bis(diphenylphosphino)benzene (dppbz) give the N-heterocyclic carbene (NHC)-diphosphine-rhodium(I) complexes: RhCl(NHC)[Ph ₂P(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.