SYNTHESIS AND STRUCTURAL STUDIES OF COMPLEXES OF VANADIUM(II) AND VANADIUM(III) HALIDES WITH TERTIARY PHOSPHINES

The vanadium(II) halides [VCl2(H2O)4] and [V(H2O)6]Br2, prepared from the metal and the appropriate acid, combine with 1,2-bis(dimethylphosp hino)ethane (dmpe) and 1,2-bis(diethylphosphino)ethane (depe) in metha nol to give [VX2(dmpe)2] and [VX2(depe)2] (X=Cl or Br). The iodo compl exes were obtained from [V(MeOH)6]I2, although [VI2(depe)2] was not pu re. The complexes [VX2(dppe)2].2thf (X=Cl or Br; dppe=1,2-bis(diphenyl phosphino)ethane) could not be isolated from methanol, but were obtain ed from tetrahydrofuran (thf). All are typical vanadium(II) complexes, and [VCl2(depe)2] and [VCl2(dppe)2].2thf have trans structures. The V -Cl bond distances, 2.445(2) and 2.420(1) angstrom, respectively, are similar to that in the known complex [VCl2(dmpe)2], but the V-P bond d istances are longer by approximately 0.06 angstrom and the P-V-P angle s are smaller by c. 3-degrees, possibly due to the steric crowding of the more heavily substituted depe and dppe ligands in the equatorial p lane. Some new complexes [VX3(PR3)n] (X = Cl or Br, PR, = monotertiary phosphine, n = 2 or 3) were also prepared from [VX3(thf)3].