C–H bond activation reactions by TpMe2Ir(iii) centres. Generation of Fischer-type carbenes and development of a catalytic system for H/D exchange

Abstract

The unsaturated [Tp^Me2Ir(C₆H₅)₂] fragment, readily generated from [Tp^Me2Ir(C₆H₅)₂(N₂)], or from [Tp^Me2Ir(C₂H₄)₂] and C₆H₆, is able to induce the regioselective cleavage of two sp³ C–H bonds of anisole, with formation of a Fischer-type carbene, 1. The process involves additionally ortho-metallation of the anisole aromatic ring, hence three C–H bonds are sequentially broken, the last one in the course of an α-H elimination reaction. Phenetole (ethyl phenyl ether) gives an analogous product, 3, despite the possibility of competitive α- or β-H eliminations in the last step. For C₆H₅NMe₂, two hydride-carbenes, 5a and 5b, are produced. In the latter, the aniline phenyl ring is also metallated, but the former contains a C₆H₅ aryl group and a C₆H₅N(Me)CH carbene ligand. The same Ir(III) fragment, viz. [Tp^Me2Ir(C₆H₅)₂], alternatively generated from C₆H₆ and [Tp^Me2Ir(η⁴-CH₂C(Me)C(Me)CH₂)], accomplishes the efficient, catalytic H/D exchange between C₆D₆ (used as the deuterium source) and a variety of organic and organometallic molecules that contain C–H bonds of different nature.