Synthesis, structure and catalytic activity of the first iridium(I) siloxide versus chloride complexes with 1,3-mesitylimidazolin-2-ylidene ligand

The first iridium(I) complex containing siloxyl and N-heterocyclic carbene ligand such as Ir(cod)(IMes)(OSiMe₃)] (1) and Ir(CO)₂(IMes)(OSiMe₃)] (3) have been synthesized and their structures solved by spectroscopy and X-ray methods as well as catalytic properties in selected hydrogenation reactions have been presented in comparison to their chloride analogues, i.e. Ir(Cl)(cod)(IMes)] (2) and Ir(Cl)(CO)₂(IMes)] (4). The attempts at synthesis of iridium(I) complex with tert-butoxyl ligand has failed as leading instead to the iridium hydroxide complex Ir(cod)(OH)(IMes)] (5) whose X-ray structure has also been solved. All complexes (1)-(5) show square planar geometry typical of the four-coordinated iridium complexes. Catalytic activity of complexes 1 and 2 was tested in transfer hydrogenation of acetophenone and hydrogenation of olefins.