Tetra(isocyanide)iridium(I) cations obtained from poly(tricarbonyl-chloroiridium)
Abstract
Poly(tricarbonylchloroiridium), [{Ir(CO)3Cl}n], reacts with alkyl and aryl isocyanides to give tetra(isocyanide)-iridium(I) cations, [Ir(CNR)4]+(I; R = C6H11, p-MeC6H4, or p-MeOC6H4). I.r. spectra support a square-planar structure for these complexes. No five-co-ordinate compound has been obtained by treating (I) with CO, PPhMe2, or RNC and no neutral four-co-ordinate compounds were isolated in the reaction with Cl–. A comparison between the reactivity of (I) and cationic dicarbonyl(phosphine)iridium(I) complexes is also made. Complexes (I) undergo oxidative addition to give cationic six-co-ordinate iridium(III) species through trans-addition. This process is easier for the alkyl than the aryl isocyanide derivatives. A comparison is made between the reactivity of (I) towards oxidative addition and that of other cationic and neutral iridium(I) complexes.