Intramolecular C-H oxidative addition to iridium(I) in complexes containing a N,N'-diphosphanosilanediamine ligand.

The iridium(I) complexes of formula Ir(cod)(SiNP)(+) (1(+)) and IrCl(cod)(SiNP) (2) are easily obtained from the reaction of SiMe2{N(4-C6H4CH3)PPh2}2 (SiNP) with [Ir(cod)(CH3CN)2](+) or [IrCl(cod)]2, respectively. The carbonylation of [1][PF6] affords the cationic pentacoordinated complex [Ir(CO)(cod)(SiNP)](+) (3(+)), while the treatment 2 with CO gives the cation 3(+) as an intermediate, finally affording an equilibrium mixture of IrCl(CO)(SiNP) (4) and the hydride derivative of formula IrHCl(CO)(SiNP-H) (5) resulting from the intramolecular oxidative addition of the C-H bond of the SiCH3 moiety to the iridium(I) center. Furthermore, the prolonged exposure of [3]Cl or 2 to CO resulted in the formation of the iridium(I) pentacoordinated complex Ir(SiNP-H)(CO)2 (6). The unprecedented κ(3)C,P,P' coordination mode of the [SiNP-H] ligand observed in 5 and 6 has been fully characterized in solution by NMR spectroscopy. In addition, the single-crystal X-ray structure of 6 is reported.