Ruthenium Dihydrogen Complex for C–H Activation: Catalytic H/D Exchange under Mild Conditions

Catalytic H/D‐exchange reactions were studied with [Ru(dtbpmp)(η 2 ‐H 2 )(H) 2 ] ( 1 ) as catalyst. Under mild reaction conditions (25–75 °C) a wide range of arenes and olefins undergo H/D exchange with [D 6 ]benzene. A preference for protons at sp 2 carbons was observed with conversions up to >90 % and significant regioselectivity in certain cases. For more reaction insights NMR‐based kinetic studies were performed with naphthalene as substrate, revealing an activation energy of 15.8 kcal mol –1 for the H/D exchange at the β‐position. Furthermore, the key steps of the reaction mechanism were investigated by means of DFT calculations for both model complexes (PMe 2 donor sites) and real catalysts (P t Bu 2 donor sites). The calculations resulted in Gibb's free activation energies in the range of 10–16 kcal mol –1 , indicating H/D exchange at the β‐position of naphthalene to be clearly favoured over the α‐position, which is in full accordance with the experimental observations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)