Synthesis and characterisation of a phosphido-bridged ruthenium cluster: crystal and molecular structure of [Ru5C(µ-H)(µ-PPh2)(CO)13]

Abstract

The complex [Ru₅C(µ-H)(µ-PPh₂)(CO)₁₃](3) has been prepared in a two-step synthesis from [Ru₅C(CO)₁₅] and PPh₂H and crystallises in the monoclinic space group C2/c, with a= 24.236(7), b= 9.699(2), c= 27.424(5)Å, β= 99.54(2)°, and Z= 8. The structure was refined to R= 0.0535 for 4 551 observed reflections. In the crystal, the complex contains a square pyramid of ruthenium atoms with the phosphido group bridging a basal edge [Ru-P 2.298(2), 2.314(2)Å]. The bridged edge [2.721(1)Å] is 0.15 Å shorter than any other basal Ru–Ru distance in the metal cage. An analogue of (3) was prepared from PPh(H)CH₂CH₂Si(OEt)₃ and [Ru₅C(CO)₁₅]. The limiting low-temperature ¹³C n.m.r. Spectrum of this complex, (5), showed the absence of any symmetry in solution and at least three CO-exchange processes at higher temperature. Complex (5) was tethered to silica and alumina via the silyl group. While (5) was reasonably stable on silica, decomposition on alumina occurred readily.