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)A, 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)A. 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)A, 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)A] 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)A, 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)A], 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)A] 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)A, 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)].