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(PPh3)}(µ-I)]

Abstract

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(PPh₃)}(µ-I)](12), which has been characterised crystallographically, crystallising in space group P 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 P 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)].