Structure and Reactivity of New Iridium Complexes with Bis(Oxazoline)-Phosphonito Ligands

The synthesis and characterization of novel iridium(I) complexes bearing a neutral bis(oxazoline)phosphonite ligand, NOPONMe2 (I), are reported. Numerous Ir(I) complexes have been isolated in high yields and characterized by spectroscopy and X-ray diffraction. [Ir(mu-Cl)(cod)](2) (cod = 1,5-cyclooctadiene) reacted with I to give the air-sensitive complex [IrCl(cod)(NOPONMe2)] (1), which shows broad H-1 and C-13{H-1} NMR signals due to dynamic exchange equilibria involving the cod and the NOPONMe2 ligands. Reaction between a solution of 1 and CO afforded the carbonyl complex [IrCl(CO)(NOPONMe2)] (2), whose solid-state structure has been determined by X-ray diffraction. Cationic complexes have been obtained by using NaBArF (BArF = B[3,5-(CF3)(2)C6H3](4)) as a chloride abstractor. The complex [Ir(cod)(NOPONMe2)]BArF (3) displays a mononuclear structure in the solid state with ligand I acting as a bidentate P,N chelating ligand. This complex is a precatalyst for the hydrogenation of alkenes. Oxidative addition of H-2 to 3 occurred either in solution or in the solid-state and this reaction allowed the isolation of the 32 electron, dinuclear dihydrido-bridged iridium(III) complex [IrH(mu-H)(NOPONMe2)](2)(BArF)(2) (4), in which the NOPONMe2 ligands exhibit a facial coordination mode. It contains only hydrides as bridging ligands and the Ir-2(mu-H)(2) unit can be viewed as containing a formal Ir-Ir double bond or two 3c-2e bonds. Complex 3 has also been reacted with CO in solution and in the solid state, and this yielded the dicarbonyl derivative [Ir(CO)(2)(NOPONMe2)]BArF (5). A transmetalation reaction between 3 and [PdCl2(NCPh)(2)] afforded the cationic Pd(II) complex [PdCl(NOPONMe2)]BArF (6), which has been structurally characterized.