Probing Highly Selective H/D Exchange Processes with a Ruthenium Complex through Neutron Diffraction and Multinuclear NMR Studies.

Deuterium labeling is a powerful way to gain mechanistic information in biology and chemistry. However, selectivity is hard to control experimentally, and labeled sites can be difficult to assign both in solution and in the solid state. Here we show that very selective high-deuterium contents can be achieved for the polyhydride ruthenium phosphine complex [RuH₂(H₂)₂(PCyp₃)₂] (<b>1</b>) (PCyp₃ = P­(C₅H₉)₃). The selectivity of the H/D exchange process is demonstrated by multinuclear NMR and neutron diffraction analyses. It has also been investigated through density functional theory (DFT) calculations. The reactions are performed under mild conditions at room temperature, and the extent of deuterium incorporation, involving selective C–H bond activation within the cyclopentyl rings of the phosphine ligands, can easily be tuned (solvent effects, D₂ pressure). It is shown that D₂ gas can inhibit the C–H/C–D exchange process