Synthesis and some reactivity of cationic alkyl nitrosyl iridium(III) derivatives

The iridium(III) dimethyl derivatives [Ir(Me)2Cp*(L)] (Cp*=η5-C5Me5; L=PPh3 (1a), PMePh2 (1b), PMe2Ph (1c), PMe3 (1d)) react with NOBF4 in CH2Cl2 to give the iridium(III) cationic alkylnitrosyl derivatives [Ir(Me)2Cp*(NO)]BF4 (2), and [Ir(Me)Cp*(NO)(L)](BF4)2 (L=PMePh2 4b, PMe2Ph 4c, PMe3 4d). EPR spectroscopy shows that the reaction proceeds through the iridium(IV) intermediates 1a+–1d+. Treatment of 1d with NOBF4 in acetonitrile gives, in addition to 4d, the acetonitrile substitution products [Ir(Me)Cp*(CH3CN)(PMe3)]BF4 (5d) and [IrCp*(CH3CN)2(PMe3)](BF4)2 (6d). Electrochemical and chemical reduction of 4b–4d afford the corresponding [Ir(Me)Cp*(NO)(L)](BF4) 7b–7d, which have been studied by EPR spectroscopy. Reaction of 2 with PPh3 gives [Ir(Me)2Cp*(PPh3)]; treatment of 4b and 4c with the appropriate phosphine gives [Ir(Me)Cp*(L)2](BF4) (L=PMePh2, PMe2Ph), respectively.