Blazina, Damir, Dunne, John P., Aiken, Stuart, Duckett, Simon B., Elkington, Charlotte, McGrady, John E., Poli, Rinaldo, Walton, Sue J., Anwar, M. Sabieh, Jones, Jonathan A., and Carteret, Hilary A.
The synthesis, characterisation and thermal and photochemical reactivity of Ru(CO)2(PPh3)(dppe) 1towards hydrogen are described. Compound 1proved to exist in both fac(major) and merforms in solution. Under thermal conditions, PPh3is lost from 1in the major reaction pathway and the known complex Ru(CO)2(dppe)(H)22is formed. Photochemically, CO loss is the dominant process, leading to the alternative dihydride Ru(CO)(PPh3)(dppe)(H)23. The major isomer of 3, viz. 3a, contains hydride ligands that are transto CO and transto one of the phosphorus atoms of the dppe ligand but a second isomer, 3b, where both hydride ligands are transto distinct phosphines, is also formed. On the NMR timescale, no interconversion of 3aand 3bwas observed, although hydride site interchange is evident with activation parameters of ΔH‡= 95 ± 6 kJ mol−1and ΔS‡= 26 ± 17 J K−1mol−1. Density functional theory confirms that the observed species are the most stable isomeric forms, and suggests that hydride exchange occurs viaa transition state featuring an η2-coordinated H2unit.