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Ligand Exchange or Reduction at Multiply Bonded Dimetal Units of Molybdenum and Rhenium by
F. Albert Cotton1, Evgeny V. Dikarev, Glenn T. Jordan IV
1Laboratory for Molecular Structure and Bonding, Department of Chemistry, Texas A&M University, P.O. Box 300012, College Station, Texas 77842-3012, and Department of Chemistry, Universidad de Costa Rica, Ciudad Universitaria, Costa Rica.
Abstract:
Reaction of 2,6-bis(diphenylphosphino)pyridine (bdppp or (Ph(2)P)(2)Py)) with K(4)Mo(2)Cl(8) in refluxing methanol gives Mo(2)Cl(4)(bdppp)(2) (1) with retention of the quadruple Mo-Mo bond. However, the quadruply bonded octachlorodirhenate(III) anion, Re(2)Cl(8)(2)(-), reacts with bdppp under similar conditions to afford Re(2)Cl(4)(bdppp)(2) (2), which has a triply bonded dirhenium(II) core, Re(2)(4+). An intermediate species, [Bu(n)(4)N][Re(2)Cl(7)(bdppp)] (3), containing an Re(2)(6+) core and only one bridging bdppp ligand has also been isolated. The crystal structures of complexes 1-3 have been investigated by X-ray crystallography. In all cases the potentially tridentate bdppp acts as a bidentate ligand using one N and one of the P atoms, leaving the second phosphorus atom noncoordinated. The crystallographic parameters for these structures are as follows: Mo(2)Cl(4)(bdppp)(2).2CH(2)Cl(2) (1.2CH(2)Cl(2)), monoclinic space group P2(1)/c with a = 15.475(2) Å, b = 11.5958(7) Å, c = 16.7637 (6) Å, beta = 98.178(5) degrees, Z = 2; Re(2)Cl(4)(bdppp)(2) (2), monoclinic space group P2(1)/n with a = 16.173(2) Å, b = 11.285(1) Å, c = 28.771 (4) Å, beta = 96.17(1) degrees, Z = 4; [Bu(n)(4)N][Re(2)Cl(7)(bdppp)].CH(2)Cl(2) (3.CH(2)Cl(2)), triclinic space group P&onemacr; with a = 16.054(2) Å, b = 18.562(3) Å, c = 20.205 (6) Å, alpha = 89.71(2) degrees, beta = 73.21(1) degrees, gamma = 73.47(2) degrees, Z = 4.