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

Abstract

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 ų, D_m= 1.48, D_c= 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-K_α 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.