Intramolecular C–H oxidative addition to iridium(i) triggered by trimethyl phosphite in N,N′-diphosphanesilanediamine complexes

Abstract

The reaction of [Ir(SiNP)(cod)][PF₆] ([1][PF₆]) and of IrCl(SiNP)(cod) (5) (SiNP = SiMe₂{N(4-C₆H₄CH₃)PPh₂}₂) with trimethyl phosphite affords the iridium(III) derivatives of the formula [IrHCl_x(SiNP-H){P(OMe)₃}_2−x]^(1−x)+ (x = 0, 3⁺; x = 1, 6) containing the κ³C,P,P′-coordinated SiNP-H ligand (SiNP-H = Si(CH₂)(CH₃){N(4-C₆H₄CH₃)PPh₂}₂). The thermally unstable pentacoordinated cation [Ir(SiNP){P(OMe)₃}(cod)]⁺ (2⁺) has been detected as an intermediate of the reaction and has been fully characterised in solution. Also, the mechanism of the C–H oxidative addition has been elucidated by DFT calculations showing that the square planar iridium(I) complexes of the formula [IrCl_x(SiNP){P(OMe)₃}_2−x]^(1−x)+ (x = 0, 4⁺; x = 1, 7) should be firstly obtained from 2⁺ and finally should undergo the C–H oxidative addition to iridium(I) via a concerted intramolecular mechanism. The influence of the counterion of 2⁺ on the outcome of the C–H oxidative addition reaction has also been investigated.