Iridium(I)– and Rhodium(I)–Olefin Complexes Containing an α-Diimine Supporting Ligand

Abstract

Iridium(I) complexes of the type IrX(olefin)(α-diimine) (α-diimine = 1,4-bis(2,6-xylyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; X = Cl, I, Me, O₂CCF₃; olefin = ethylene, cyclooctene (COE)) were synthesized from the readily available precursor [IrCl(COE)₂]₂. These complexes display unusual ¹H NMR spectra and have large UV-vis extinction coefficients. NOESY and HSQC NMR experiments were used to provide rigorous NMR spectral assignments, and IrCl(C₂H₄)(α-diimine), 1, and IrCl(COE)(α-diimine), 4, were structurally characterized by X-ray crystallography. The related rhodium complex [RhCl(α-diimine)]₂, 6, was also synthesized and characterized by NMR and X-ray crystallography. 6 was observed to be in equilibrium with RhCl(C₂H₄)(α-diimine), 7, under an ethylene atmosphere.