Improved syntheses of the hexanuclear clusters [Ru6(CO)18]2-, [HRu6(CO)18]- and [H2Ru6(CO)18]. The x-ray analysis of [HRu6(CO)18]-, a polynuclear carbonyl containing an interstitial hydrogen ligand

The X-ray analyses of two crystalline modifications, (I) and (II), of [N(PPh3)2][HRu6(CO)18] are reported, together with improved synthetic routes to this and the related clusters [Ru6(CO)18]2- and H2Ru6(CO)18. Crystals of (I) are triclinic, space group P1, with a = 18.083(4), b = 19.101(4), c = 19.238(5) Å, α = 117.70(4), β = 78.13(2), γ = 97.05(2)°, and Z = 4. Crystals of (II) are monoclinic, space group P21/n, with a = 33.82(8), b = 52.55(10), c = 9.832(2) Å;, β = 92.66(2)°, and Z = 12. Least-squares refinement using diffractometer data (Mo-Kα) has given an R of 0.068 1 for 9 165 reflections for (I) and an R of 0.23 (Ru only) for 1 485 reflections for (II). The unit cell in (I) contains two independent molecules of [HRu6(CO)18]-, cluster (1) which is ordered and cluster (2) which is disordered between two sites (2A) and (2B) that are related by a non-crystallographic two-fold axis. The combined evidence of the X-ray analyses, 1H n.m.r. studies, i.r. [v(CO)] spectra, and variable-temperature 13C n.m.r. is only consistent with the hydrogen ligand lying inside the Ru6 octahedron.