1Pyridine and phosphine functionalised N-heterocyclic carbene complexes of rhodium and iridium

Abstract

The pyridine functionalised N-heterocyclic carbene complexes [M(κ 2-NC DIPP)(COD)] +A −, NC DIPP = 3 - ( 2 , 6 - Pr 2 i C 6 H 3 ) - 1 - [ 2 - ( 3 - picolyl ) ] - imidazol - 2 - ylidene , A - = [ Ar 4 F B ] - , [{3,5-(CF 3) 2C 6H 2} 4B] −, M = Rh, 1b, Ir, 4, have been prepared in two steps by reaction of the [M(COD)Cl] 2 with the isolated NC DIPP to [Rh(κ 1-NC DIPP)(COD)Cl], 2, and [Ir(κ 2-NC DIPP)(COD)Cl], 3, followed by anion exchange with Na +A −. The phosphine functionalised N-heterocyclic carbene complex [Rh(PCH 2C mes) 2]Br, 6, PCH 2C mes = 1-(diphenylphosphino-methyl)-3-(2,4,6-Me 3C 6H 2)-imidazol-2-ylidene, was prepared by the reaction of the [Rh(COD)Cl] 2 with the corresponding N-heterocyclic carbene generated in situ. Monomeric [Rh(PCH 2CH 2C DIPP)(acac)], 7 was prepared by an analogous reactions from [Rh(COE) 2(acac)]. In contrast, phosphine functionalised N-heterocyclic carbene complexes of iridium (I) were not easily accessible. However, the reaction of [Ir(COD)(μ-Cl)2(μ-H)]2 with PCH 2CH 2C mes gave complex [Ir(COD)(PCH 2CH 2C mes )Br], 8, in which the carbene is coordinated to the metal in an ‘abnormal’ mode.