Coordination Versatility of Pyridine-Functionalized N-Heterocyclic Carbenes: A Detailed Study of the Different Activation Procedures. Characterization of New Rh and Ir Compounds and Study of Their Catalytic Activity

Three different reaction procedures for the coordination of N-n-butyl-N‘-(2-pyridylmethyl)imidazolium salt have produced
new N-heterocyclic complexes of Rh and Ir. The direct reaction of the imidazolium salt with [IrCl(cod)]2 provides a
NHC−IrIII−H complex, while transmetalation from a silver−NHC complex and deprotonation with NEt3 give new
NHC complexes of M(I) and M(III) when reacting with [MCl(cod)]2 or [MCl(coe)2]2 (M = Rh, Ir). The crystal structures
of the biscarbene Rh(III) and Ir(III) complexes are described. The catalytic properties of the compounds obtained
have been tested in the hydrosilylation of acetylenes, the cyclization of acetylenic carboxylic acids, and hydrogen
transfer to ketones.