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

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, O 2 CCF 3 ; olefin = ethylene, cyclooctene (COE)) were synthesized from the readily available precursor [IrCl(COE) 2 ] 2 . These complexes display unusual 1 H NMR spectra and have large UV-vis extinction coefficients. NOESY and HSQC NMR experiments were used to provide rigorous NMR spectral assignments, and IrCl(C 2 H 4 )(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(C 2 H 4 )(α-diimine), 7 , under an ethylene atmosphere.