SCHEDULED MAINTENANCE
A combined parahydrogen and theoretical study of H2 activation by 16-electron d8 ruthenium(0) complexes and their subsequent catalytic behaviour†
Abstract
The photochemical reaction of Ru(CO)3(L)2, where L = PPh3, PMe3, PCy3 and P(p-tolyl)3 with parahydrogen (p-H2) has been studied by in-situ NMR spectroscopy and shown to result in two competing processes. The first of these involves loss of CO and results in the formation of the cis-cis-trans-L isomer of Ru(CO)2(L)2(H)2, while in the second, a single photon induces loss of both CO and L and leads to the formation of cis-cis-cis Ru(CO)2(L)2(H)2 and Ru(CO)2(L)(solvent)(H)2 where solvent = toluene, THF and pyridine (py). In the case of L = PPh3, cis-cis-trans-L Ru(CO)2(L)2(H)2 is shown to be an effective hydrogenation catalyst with rate limiting phosphine dissociation proceeding at a rate of 2.2 s−1 in pyridine at 355 K. Theoretical calculations and experimental observations show that H2 addition to the Ru(CO)2(L)2 proceeds to form cis-cis-trans-L Ru(CO)2(L)2(H)2 as the major product via addition over the π-accepting OC–Ru–CO axis.
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