Cationic ruthenium systems. Part 2. Synthesis, characterization, and X-ray structure of hydridopentakis(dimethylphenylphosphine)-ruthenium(II) hexafluorophosphate: a discussion of the effects of steric strains on the reactivity of the complex
The complex [RuH(PMe2Ph)5][PF6] has been prepared by treatment of a methanolic solution of [RuH(cod)(NH2-NMe2)3][PF6](cod = cyclo-ocata-1,5-diene) with PMe2Ph under argon and has been characterized by microanalytical, i.r., and 1H n.m.r. data and by a three-dimensional X-ray structure determination. The colourless crystals of [RuH(PMe2Ph)5][PF6], M= 938, are orthorhombic, space group P212121, a= 21.55(3), b= 19.08(3), c= 10.38(2)Å, U= 4 269 Å3, Dm= 1.48, Dc= 1.46 g cm–3, Z= 4. The structure has been solved by the heavyatom method and refined by least squares to R 0.061 for 1 954 observed reflections collected on a diffractometer using graphite-monochromatized Mo-Kα radiation. The co-ordination about the ruthenium is distorted octahedral. The length of the bond to the phosphine trans to the hydride ligand (Ru–P 2.48 Å) is significantly longer than those to the other four phosphine ligands (mean Ru–P 2.40 ± 0.01 Å). There is considerable strain within the cation caused by non-bonded repulsions between the methyl and phenyl groups on different phosphine ligands. A discussion of the build-up of steric strain in co-ordination complexes containing PMe2Ph ligands is presented.