The synthesis and characterisation of the following trimethylphosphine stabilised hydride and hydroxo-compounds of ruthenium and reported; (Me₃P)₃ HRu(µ-H)₂ RuH(PMe₃)₃, (1), [Ru₂(µ-H)₃(PMe₃)₆][BF₄], (2), Ru₂(µ-H)-(µ-OH)(PMe₃)₆, cis-RuH₂(PMe₃)₄, and Ru₂(OH)₄(PMe₃)₆. The compounds have been studied by i.r. and n.m.r. (¹H and ³¹P) spectroscopy; for Ru₂(µ-H)(µ-OH)(PMe₃)₆ a multinuclear n.m.r. study (¹H, ¹³C, and ³¹P) has been made.

The structures of Ru₂H₄(PMe₃)₆, (1), and [Ru₂(µ-H)₃(PMe₃)₆][BF₄], (2), have been determined by single-crystal X-ray diffraction methods. Compound (1) is triclinic, space group P, with a= 9.277, b= 15.861, c= 17.958 Å, α= 110.13, β= 94.59, γ= 90.61°, and Z= 3. The structure was refined to an R of 0.049 for 7 744 observed reflections measured on a diffractometer. The unit cell contains three molecules, one having crystallo-gaphic symmetry, the others lying in symmetry related general positions. The molecular structures of the crystallographically independent molecules are very similar and are probably chemically equivalent, although the hydride atoms were not all located. The Ru–Ru distances are identical, at 2.811(1)Å, and the Ru–P bond lengths show a consistent trend, with those trans to the terminal hydrides longer (ca. 2.35 Å) than the others (ca. 2.23–2.24 Å). Compound (2) is monoclinic, space group P2/n, with a=15.087, b= 9.796, c= 12.330 Å, β= 108°, and Z= 2.The structure was refined to an R of 0.046 for 3 774 observed data. The cation in (2) has C₂ symmetry with one bridging hydride lying on the symmetry axis. The Ru–Ru distance is 2.540(1)Å and the three independent Ru–P lengths are equal at ca. 2.265(1)Å. The hydride atoms were all located and refined, giving Ru–H distances of ca. 1.9 Å.