Octacarbonyldi-μ2-hydrido-[μ3-(1,3,5-trimethylphenyl)phosphinidene](triphenylphosphane)-triangulo-triruthenium

In the crystal structure of the title compound, [Ru3(C9H11P)H2(C18H15P)(CO)8], the triangular Ru3 unit is capped with one mesitylphosphinidene ligand. In the trigonal–pyramidal Ru3P core, one RuII atom is coordinated by a triphenylphosphane ligand in a terminal fashion. Two hydride ligands bridge over two Ru—Ru bonds. These Ru—Ru bonds [2.9400 (4) and 2.9432 (4) Å] are slightly longer than the nonhydride-bridged Ru—Ru bond [2.8146 (4) Å]. The terminal triphenylphosphane ligand coordinates to the RuII atom, which is involved in two hydride bridges.

In the crystal structure of the title compound, [Ru 3 (C 9 H 11 P)-H 2 (C 18 H 15 P)(CO) 8 ], the triangular Ru 3 unit is capped with one mesitylphosphinidene ligand. In the trigonal-pyramidal Ru 3 P core, one Ru II atom is coordinated by a triphenylphosphane ligand in a terminal fashion. Two hydride ligands bridge over two Ru-Ru bonds. These Ru-Ru bonds [2.9400 (4) and 2.9432 (4) Å ] are slightly longer than the nonhydride-bridged Ru-Ru bond [2.8146 (4) Å ]. The terminal triphenylphosphane ligand coordinates to the Ru II atom, which is involved in two hydride bridges.
The 31 P NMR spectrum shows the signals of µ 3 -PMes and PPh 3 ligands at a low field (231.3 ppm) and a moderately high field (34.7 ppm), respectively.

Experimental
All reactions were performed under a dry nitrogen atmosphere or a high vacuum. Toluene and hexane were distilled from sodium-benzophenone ketyl just before use. A toluene solution (2 ml) of [Ru 3 (CO) 9 (µ-H) 2 (µ 3 -PMes)] (25 mg, 0.035 mmol) and PPh 3 (10 mg, 0.038 mmol) was photolysed for 3 h with a 450 W medium pressure Hg arc lamp with stirring at 6°C. During the photo-irradiation, the evolved CO in the reaction vessel was removed by freeze-pump-thaw cycles every 1 h. After the photolysis, the solvent was filtered and evaporated to dryness under a high vacuum. Recrystallization of the residue from hexane at -30°C gave the title compound (29 mg, 0.031 mmol, 88%) as yellow platelets.
Spectral data for the title compound

Refinement
The positions of two hydrogen atoms bridging Ru-Ru bonds were found on the difference Fourier synthesis and refined with isotropic thermal parameters. All other hydrogen atoms were placed at their geometrically calculated positions with C-H = 0.95 and 0.98 Å and with U iso (H) values of 1.2 and 1.5 times U eq (C). ; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figure 1
A molecular structure of the title compound, with atom labels and 50% probability displacement ellipsoids for non-H atoms.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.