Transition-metal complexes containing phosphorus ligands. Part V. Synthesis and reactivity of some iridium triaryl phosphite complexes: metal-assisted cleavage of ortho-carbon–hydrogen bonds in co-ordinated triaryl phosphite ligands

Abstract

The synthesis and isolation of some triaryl phosphite complexes of iridium-(I) and -(III), IrCl(CO)[P(OAr)₃]₂ and IrHX₂[P(OAr)₃]₃(X = Cl, Br, I; Ar = aryl) are described. Evidence for the formation in solution of other iridium triaryl phosphite complexes including IrX[P(OAr)₃]₃(X = OMe, Cl, Br) and IrH(CO)[P(OPh)₃]₃ is presented. These complexes are shown to undergo intramolecular, ligand–metal, hydrogen transfer and elimination reactions involving cleavage of aryl ortho-carbon hydrogen bonds with concomitant formation of products containing metal-ortho-carbon bonds. Successive reactions of this type lead to products containing one, two and three iridium carbon bonds per molecule, and afford the most extensive series of metal ortho-carbon bond formation reactions reported to date. The course of these reactions has been followed by use of infrared and high-field n.m.r. spectroscopy, the former to detect the presence of metal ortho-carbon bonded chelate P(OPh)₂(OC₆H₄) ligands, the latter to identify the nature and stereochemistry of hydridic reaction products. Confirmatory evidence concerning the nature of these reactions has been obtained wherever possible by isolation, analysis and characterisation of solid products.