Reactions of [Ru₅C(CO)₁₅] involving bridging ligands: Crystal and molecular structures of the complexes [Ru₅(H)C(CO)₁₄(SEt)], [Ru₅(H)C(CO)₁₃(PPh₃)(SEt)], [Ru₅(H)C(CO)₁₂(PPh₃)(SEt)], and [Ru₅C(CO)₁₃(PPh₃){μ-Au(PPh ₃)}(μ-I)]

The cluster [Ru₅C(CO)₁₅] reacts with H₂S, H₂Se, and HSR (R = Me or Et) to give [Ru₅(H)C(CO)₁₄(SH)], [Ru₅(H)C(CO)₁₄(SeH)], and [Ru₅(H)C(CO)₁₄(SR)], respectively. The complex [Ru₅(H)C(CO)₁₄(SEt)] crystallises in space group P2₁/n with a = 15.315(3), b = 16.739(4), c = 10.286(3) Å, β = 89.31(2)°, and Z = 4. The structure was solved by a combination of direct methods and Fourier-difference techniques, and refined by blocked-cascade least squares to R = 0.032 for 4134 observed diffractometer data. The Ru₅ metal arrangement is intermediate between a square-based pyramid and a bridged 'butterfly' with a carbido-carbon at the centre of the cluster. The sulphur atom of the SEt group bridges one edge of the square pyramid where the Ru ⋯ Ru separation is 3.410(1) Å. In the reaction of [Ru₅C(CO)₁₅] with HSEt the postulated intermediate [Ru₅(H)C(CO)₁₅(SEt)] was not isolated. The first product was [Ru₅(H)C(CO)₁₄(SEt)] (4). When (4) is heated to 81 °C a further molecule of CO is lost and the complex [Ru₅(H)C(CO)₁₃(SEt)] isolated. A phosphine derivative of this complex was also prepared and characterised crystallographically; [Ru₅(H)C(CO)₁₃(PPh₃)(SEt)] (6) crystallises in space group P2₁/c with a = 15.892(2), b = 11.474(1), c = 21.387(2) Å, β = 92.50(1)°, and Z = 4. The structure was solved and refined using the same techniques as for (4) to R = 0.036 for 5 861 reflections. The structure resembles that of (4) with the SEt group bridging a long Ru ⋯ Ru edge [3.438(1) Å] but with one of the carbonyl groups on a Ru atom associated with the SEt bridge replaced by a phosphine ligand. An analogous reaction occurs when [Ru₅C(CO)₁₄{μ-Au(PPh₃)}(μ-I)] is heated in heptane to give [Ru₅C(CO)₁₃{μ-Au(PPh₃)}(μ-I)]. This complex also readily takes up phosphine to give [Ru₅C(CO)₁₃(PPh₃){μ-Au(PPh ₃)}(μ-I)] (12), which has been characterised crystallographically, crystallising in space group P1̄ with a = 9.899(3), b = 14.628(6), c = 18.788(7) Å, α = 100.29(3), β = 91.31(3), γ = 93.69(3)°, and Z = 2. The structure was solved and refined as described above to R = 0.042 for 6 075 reflections. The general geometry of the Ru₅C core observed in (6) is retained and the iodine ligand bridges a long Ru ⋯ Ru edge [3.526(1) Å], and the Au(PPh₃) group replaces the bridging hydride. Further heating of the cluster (6) results in the loss of a further CO ligand to give [Ru₅(H)C(CO)₁₂(PPh₃)(SEt)] (7) which may exist in two isomeric forms. The structure of one of the isomers shows that Ru-Ru bond formation has occurred and the geometry of the Ru₅C core may be described as a centred, square-based pyramid. The SEt group now bridges a basal Ru-Ru edge [2.698(1) Å] and the phosphine ligand is co-ordinated to a basal Ru atom. The complex (7) crystallises in space group P1̄ with a = 10.162(2), b = 13.807(4), c = 14.660(4) Å, α = 78.20(2), β = 74.12(2), γ = 87.38(2)°, and Z = 2. This converged to R = 0.041 for 4 050 reflections. The adducts [Ru₅C(CO)₁₅{μ-Au(PPh₃)}X] (X =Cl or Br) and their derivatives [Ru₅C(CO)₁₄{μ-Au(PPh₃)}X] react with PPh₃ to eliminate'Au(PPh₃)X' and produce [Ru₅C(CO)₁₄(PPh₃)].