Synthesis and Catalytic Activity of Rhodium(I) and Iridium(I) 4,5-Dibrominated N-Heterocyclic Carbenes

The synthesis and characterisation of another example of an air-stable carbene is described, in addition to the preparation of rhodium and iridium olefin and carbonyl complexes. The spectroscopic data indicates that these air-stable carbenes do not display reduced sigma-donor capacity of the carbenic centre. The catalytic applications of these carbenes are explored in the hydrosilylation and transfer hydrogenation processes.