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

Abstract

The iridium(III) dimethyl derivatives [Ir(Me) 2Cp*(L)] (Cp*=η 5-C 5Me 5; L=PPh 3 ( 1a), PMePh 2 ( 1b), PMe 2Ph ( 1c), PMe 3 ( 1d)) react with NOBF 4 in CH 2Cl 2 to give the iridium(III) cationic alkylnitrosyl derivatives [Ir(Me) 2Cp*(NO)]BF 4 ( 2), and [Ir(Me)Cp*(NO)(L)](BF 4) 2 (L=PMePh 2 4b, PMe 2Ph 4c, PMe 3 4d). EPR spectroscopy shows that the reaction proceeds through the iridium(IV) intermediates 1a + – 1d +. Treatment of 1d with NOBF 4 in acetonitrile gives, in addition to 4d, the acetonitrile substitution products [Ir(Me)Cp*(CH 3CN)(PMe 3)]BF 4 ( 5d) and [IrCp*(CH 3CN) 2(PMe 3)](BF 4) 2 ( 6d). Electrochemical and chemical reduction of 4b– 4d afford the corresponding [Ir(Me)Cp*(NO)(L)](BF 4) 7b– 7d, which have been studied by EPR spectroscopy. Reaction of 2 with PPh 3 gives [Ir(Me) 2Cp*(PPh 3)]; treatment of 4b and 4c with the appropriate phosphine gives [Ir(Me)Cp*(L) 2](BF 4) (L=PMePh 2, PMe 2Ph), respectively.