Synthesis and reactivity of some isocyanide complexes of iridium(I)

Abstract

Several isocyanide complexes [Ir(RNC)4]X (I) (R = p-CH3C6H4, X = I; R = p-CH3OC6H4, X = I and PF6) and [Ir(RNC)2(PPh3)3] ClO4(II) (R = p-CH3C6H4 and p-CH3OC6H4) have been prepared by the reactions of [Ir(COD)Cl]2 and [Ir(COD)(PPh3)2]ClO4 (COD = l,5-cyclooctadiene) with aryIisocyanides, respectively. Oxidative addition reactions of I and II with halogens, and II with π-acids such as tetracyanoethylene(TCNE), fumaronitrile, maleic anhydride, dimethyl fumarate, acrylonitrile, and dimethyl acetylenedicarboxylate are described. The structures of I, II and the π-acid addition products of II, [Ir(p-CH3C6H4NC)2 (PPh3)2 (π-acid)]ClO4 (IV) (π-acid = TCNE, fumaronitrile, maleic anhydride, and acetylene dicarboxylate), are discussed on the basis of their electronic, IR, and NMR spectra. Especially, I is suggested to have an unusual layer structure involving Ir to Ir interaction, the result of which is relatively low reactivity in oxidative addition reactions. Trigonal bipyramidal configurations are suggested for IV with the two isocyanides in the trans and cis positions for the olefin and acetylene adducts, respectively.