Dihydrogen and Hydrido Complexes via Hydrogen Addition to d6 Five-co-ordinate Complexes of Ruthenium and Osmium with 1,2-Bis(dicyclohexylphosphino)ethane

The dihydrogen complexes [MX(eta-2-H-2)(dcpe)2]BPh4 [dcpe = 1,2-bis(dicyclohexylphosphino)ethane; M = Ru, X = H or Cl; M = Os, X = Cl] were prepared by reaction of molecular hydrogen with the five-co-ordinate complexes [MX(dcpe)2]BPh4, or by protonation of the hydrides [MH(X)(dcpe)2]. The same synthetic procedures yielded [OsH3(dcpe)2]BPh4, for which a classical trihydride seven-co-ordinate structure is proposed. The compounds have been characterized by variable-temperature H-1 and P-31-{H-1} NMR spectra and T1 measurements. The reaction of molecular hydrogen with the complexes cis-[MCl2(dcpe)2] to yield trans-[MH(Cl)(dcpe)2] and cis-[MH2(dcpe)2] is also discussed.