73037-72-6Relevant academic research and scientific papers
Synthesis, crystal structure, and dynamic behavior of tetra-μ-hydrido-μ-[1,2-bis(diphenylphosphino)ethane]- decacarbonyltetraruthenium, an isomer of (μ-H)4Ru4(CO)10(diphos) with a Bridging diphos ligand
Churchill, Melvyn Rowen,Lashewycz, Romana A.,Shapley, John R.,Richter, Steven I.
, p. 1277 - 1285 (2008/10/08)
In the presence of trimethylamine oxide the substitution of (μ-H)4Ru4(CO)12 by 1-2-bis(diphenylphosphino)ethane(diphos) occurs rapidly at room temperature and leads to (μ-H)4Ru4(CO)10(μ-diphos) as the major product. Upon being heated, this compound (isomer II) rearranges to the previously characterized compound (μ-H)4Ru4(CO)10(diphos) (isomer I). Isomer II crystallizes in the centrosymmetric monoclinic space group P21/c with a = 16.845 (3) A?, b = 14.644 (2) A?, c = 17.469 (3) A?, β = 116.48 (1)°, ρ(obsd) = 1.865 (10) g cm-3 and ρ(calcd) = 1.872 g cm-3 for V = 3857 A?3, mol wt 1086.85, and Z = 4. Diffraction data were collected with Mo Kα radiation on a Syntex P21 diffractometer, and the structure was solved by conventional methods, using the Syntex XTL system. The final discrepancy indices were RF = 5.9% and RwF = 4.6% for those 2446 reflections with |Fo| > σ(Fo). All atoms, including the four bridging hydrides, were located directly. Positional parameters of the hydride ligands were refined, the resulting Ru-(μ-H) bond lengths averaging 1.70 ± 0.12 A? and the Ru-(μ-H)-Ru bond angles averaging 124 ± 9°. The hydrido-bridged ruthenium-ruthenium vectors range from 2.923 (2) to 3.048 (2) A?, while the nonhydrido-bridged Ru-Ru bonds are 2.779 (2) and 2.782 (2) A?. The diphos ligand takes up a bridging position between Ru(1) and Ru(2), the two ruthenium-phosphorus bond lengths being 2.356 (4) and 2.335 (5) A?. The (μ-H)4Ru4 core of the molecuke takes up the asymmetric (idealized Cs symmetry) form, as found in (μ-H)4Ru4(CO)10(diphos) (isomer I), rather than the symmetric (D2d) configuration found in other H4Ru4L12 species. The hydride ligands in (μ-H)4Ru4(CO)10(μ-diphos) are fluxional. Complete equilibration is evident at room temperature (τ 27.3, triplet, J = 3 Hz). Various stages of the equilibration are observable at lower temperatures, but a static spectrum was not achieved even at -131°C. Spectral changes below -70°C can be interpreted in terms of edge-to-edge movement of one hydride ligand (ΔG? = 7.2 kcal/mol) together with conformational changes in the backbone of the diphos ligand (ΔG? = 9.1 kcal/mol).
