Four-co-ordinate cationic dicarbonyl(phosphine)iridium(I) complexes obtained from chlorotricarbonyliridium

Abstract

The chlorotricarbonyliridium, [Ir(CO)₃Cl]_n, reacts, in the presence of AgBF₄ or NaBPh₄, with tertiary phosphines L [L = PPh₃, P(o-tolyl)₃, P(isopropyl)₃, P(cyclohexyl)₃, or PPh₂Bu^t] giving cationic four-co-ordinated products [Ir(CO)₂L₂]⁺. Steric rather than electronic factors seem to be very important for the formation of the above reported compounds. The complexes [Ir(CO)₂L₂]⁺[L = PPrⁱ₃, P(C₆H₁₁)₃, PPh₂Bu^t] absorb CO giving cationic five-co-ordinated compounds [Ir(CO)₃L₂]⁺; the same reaction does not occur when L = PPh₃ or P(o-tolyl)₃ and this confirms the importance of the phosphine basicity in promoting five-co-ordination. The chloride ion reacts with [Ir(CO)₂L₂]⁺ complexes giving the neutral compounds trans-Ir(CO)L₂Cl. Some oxidative addition reaction on [Ir(CO)₂L₂]⁺ complexes are described.