Highly Selective and Efficient Perdeuteration of n-Pentane via H/D Exchange Catalyzed by a Silica-Supported Hafnium-Iridium Bimetallic Complex.

A Surface OrganoMetallic Chemistry (SOMC) approach is used to prepare a novel hafnium-iridium catalyst immobilized on silica, HfIr/SiO, featuring well-defined [≡SiOHf(CH Bu)(μ-H)IrCp*] surface sites. Unlike the monometallic analogous materials Hf/SiO and Ir/SiO, which promote n-pentane deuterogenolysis through C-C bond scission, we demonstrate that under the same experimental conditions (1 bar D, 250 °C, 3 h, 0.5 mol %), the heterobimetallic catalyst HfIr/SiO is highly efficient and selective for the perdeuteration of alkanes with D, exemplified on n-pentane, without substantial deuterogenolysis (<2 % at 95 % conversion).

Mechanistic investigations via DFT support the cooperative heterobimetallic C-H and O-H bond activation across Ta[double bond, length as m-dash]Ir multiple bonds.

A rare heterobimetallic oxidative addition of X-H (X = C, O) bonds is reported. DFT suggests that steric constraints around the bimetallic core play a critical role to synergistically activate C-H bonds across the two metals and thus explains the exceptional H/D exchange catalytic activity of unhindered surface organometallic Ta/Ir species observed experimentally.

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)], .