Synthesis, NMR, and X-ray Molecular Structure of a Butadienesulfinate Iridium Dimer and Its Transformation into a Mononuclear CpIrCl[(1,2,5-η)-SO2CHCRCHCHR] Complex

A metathesis reaction of [Cp*IrCl2]2 with butadienesulfinate lithium (SO2CHCRCHCHR)Li (R = H, 1Li; Me, 2Li) affords the dinuclear compounds [Cp*Ir(Cl)2{(5-η)-SO2CHCRCHCHR}(Li)(THF)]2 (R = H, 3; Me, 4), respectively. The single-crystal X-ray analysis of 3 and 4 reveals the presence of metallacyclic, five- and eight-membered rings, which easily break to afford compounds Cp*IrCl[(1,2,5-η)-SO2CHCRCHCHR] [R = H, (5), Me (6)], upon displacement of THF and LiCl. The 1H and 13C NMR data are consistent with the single-crystal X-ray diffraction structures of 3 and 4. Compounds 5 and 6 showed that the butadienesulfonyl ligands are coordinated through the sulfur atoms and the terminal double bonds, according to the X-ray study of compound 5 and NMR spectroscopy. Immediate formation of compound 5 can be achieved in 83% yield from [Cp*IrCl2]2 and 1K, showing that the alkaline metal is crucial in the isolation of the lithium derivatives 3 and 4.