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

Abstract

The synthesis and characterization of novel iridium(I) complexes bearing a neutral bis(oxazoline)phosphonite ligand, NOPON(Me(2)) (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)(NOPON(Me(2)))] (1), which shows broad (1)H and (13)C{(1)H} NMR signals due to dynamic exchange equilibria involving the cod and the NOPON(Me(2)) ligands. Reaction between a solution of 1 and CO afforded the carbonyl complex [IrCl(CO)(NOPON(Me(2)))] (2), whose solid-state structure has been determined by X-ray diffraction. Cationic complexes have been obtained by using NaBAr(F) (BAr(F) = B[3,5-(CF(3))(2)C(6)H(3)](4)) as a chloride abstractor. The complex [Ir(cod)(NOPON(Me(2)))]BAr(F) (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)(NOPON(Me(2)))](2)(BAr(F))(2) (4), in which the NOPON(Me(2)) 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)(NOPON(Me(2)))]BAr(F) (5). A transmetalation reaction between 3 and [PdCl(2)(NCPh)(2)] afforded the cationic Pd(II) complex [PdCl(NOPON(Me(2)))]BAr(F) (6), which has been structurally characterized.