Synthesis and Derivatization of Iridium(I) and Iridium(III) Pentamethyl[60]fullerene Complexes

Abstract

An iridium(I) pentamethyl[60]fullerene complex, Ir(η5-C60Me5)(CO)2 (1), was prepared by the reaction of K(C60Me5) with [IrCl(CO)2]2 in an acetonitrile/THF solution. Oxidation of the iridium atom of 1 by I2 successfully proceeded to afford an iridium(III) complex, Ir(η5-C60Me5)I2(CO) (2), in 80% yield. Ligand exchange reactions of 1 took place to give phosphine complexes, Ir(η5-C60Me5)(CO)(PEt3) (3b) and Ir(η5-C60Me5)(CO)(PPh3) (3c), in 60% and 35% yields, respectively. Similarly, the Ir(I) phosphine complex Ir(η5-C60Me5)(CO)(PMe3) (3a) was also obtained by the reaction of 2 with PMe3 in 92% yield via reduction of the complex, while treatment of 2 with XylNC (Xyl = 2,6-dimethylphenyl isocyanide) gave another Ir(III) complex, Ir(η5-C60Me5)I2(XylNC) (4), in 93% yield. MeMgBr and PhCCMgBr reacted with 2 to give alkyl and alkynyl complexes, Ir(η5-C60Me5)Me2(CO) (5) and Ir(η5-C60Me5)(CCPh)2(CO) (6), in 60% and 81% yields, respectively. The molecular structures of 1, 2, and 3a were determined by X-ray crystallographic analysis. Cyclic voltammetric investigation of 1 and 2 revealed the electrochemical properties of the Ir(I) and Ir(III) complexes. Complex 1 showed three reversible one-electron-reduction waves in the cathodic scan, and one reversible two-electron-oxidation wave in the anodic scan, while the complex 2 exhibited two-electron reduction of the metal center and one-electron reduction of the fullerene part. The isolated diiodide complex 2 will be a useful starting material for the synthesis of various metal fullerene complexes.