RESUMEN

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.