Metal-Metal Synergy in Well-Defined Surface Tantalum-Iridium Heterobimetallic Catalysts for H/D Exchange Reactions.

A novel heterobimetallic tantalum/iridium hydrido complex, [{Ta(CHBu)}{IrH(Cp*)}] , featuring a very short metal-metal bond, has been isolated through an original alkane elimination route from Ta(CHBu)(CHBu) and Cp*IrH. This molecular precursor has been used to synthesize well-defined silica-supported low-coordinate heterobimetallic hydrido species [≡SiOTa(CHBu){IrH(Cp*)}], , and [≡SiOTa(CHBu)H{IrH(Cp*)}], , using a surface organometallic chemistry (SOMC) approach. The SOMC methodology prevents undesired dimerization as encountered in solution and leading to a tetranuclear species [{Ta(CHBu)}(Cp*IrH)], . This approach therefore allows access to unique low-coordinate species not attainable in solution. These original supported Ta/Ir species exhibit drastically enhanced catalytic performances in H/D exchange reactions with respect to (i) monometallic analogues as well as (ii) homogeneous systems. In particular, material promotes the H/D exchange between fluorobenzene and CD or D as deuterium sources with excellent productivity (TON up to 1422; TOF up to 23.3 h) under mild conditions (25 °C, sub-atmospheric D pressure) without any additives.