Coordination Chemistry of a Modular N,C-Chelating Oxazole-Carbene Ligand and Its Applications in Hydrosilylation Catalysis

Reaction of 1-mesitylimidazole with 2-chlorobenzoxazole gave the 2-benzoxazolyl imidazolium salt bzoxcarbH + Cl - ( 1 ), which was converted to the silver N-heterocyclic carbene complex [Ag I (bzoxcarb)Cl] ( 2 ) by reaction with Ag 2 O in dichloromethane. The crystal structure analysis confirmed the monomeric nature of complex 2 . The silver complex 2 was reacted with [PdCl 2 (COD)] to yield the corresponding palladium complex [PdCl 2 (bzoxcarb)] ( 3 ), for which an X-ray diffraction study established a distorted square planar configuration with the imidazolyl and the oxazolyl ring lying within the molecular plane. Upon direct reaction of the imidazolium salt 1 with Pd(OAc) 2 /NaI, a bis-carbene palladium complex [PdI 2 (bzoxcarb) 2 ] ( 4 ) was obtained. The rhodium complex [RhCl(bzoxcarb)(CO)] ( 5 ) was prepared in high yield in a one-step reaction of 1 with [Rh(acac)(CO) 2 ] (acac = acetylacetonate). The silver N-heterocyclic carbene complex 2 was also used as carbene transfer reagent in the synthesis of the platinum complex [PtCl 2 (bzoxcarb)] ( 6 ), which was found to be an active catalyst for the hydrosilylation of alkenes and alkynes.