Heterogenised N-heterocyclic carbene complexes: synthesis, characterisation and application for hydroformylation and C–C bond formation reactions

Abstract

The imidazolium salts: 1-mesityl-3-(3-trimethoxysilylpropyl)imidazolium iodide and 1-tert-butyl-3-(3-trimethoxysilylpropyl)imidazolium iodide, abbreviated as (tmpMes)HI (3a) and (tmp^tBu)HI (3b), respectively, have been synthesised. The palladium(II) complexes (η³-C₃H₅) (tmpMes)PdCl (5a) and (η³-C₃H₅)(tmp^tBu)PdCl (5b), rhodium(I) and iridium(I) complexes (η⁴-1,5-COD) (tmpMes)MCl, M = Rh (6a), Ir (7a) and (η⁴-1,5-COD)(tmp^tBu)MCl, where M = Rh (6b), Ir (7b), were synthesised by silver transmetallation reactions using the silver(I) complexes (tmpMes)AgI (4a) and (tmp^tBu)AgI (4b). The iridium complex 7b has been structurally characterised. The Pd(II) and Rh(I) complexes have been immobilised by attachment to chemically modified MCM-41. The immobilised palladium(II) materials have been tested as recyclable catalysts for Suzuki type C–C bond formation reactions in water and the immobilised rhodium(I) materials have been examined for their catalytic ability for the hydroformylation of 1-octene.