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.