SYNTHESIS AND CHARACTERIZATION OF DINUCLEAR NIOBIUM(IV) COMPLEXES WITH SYMMETRICAL AND UNSYMMETRICAL DITERTIARY PHOSPHINES

A series of dinuclear diamagnetic niobium(IV) complexes of the types Nb2Cl8[psi2-P-(CH2)n-P-phi2]2 (where n = 1 to 6), Nb2Cl8[phi2-P-CH = CH-P-phi2]2 and Nb2Cl8[(p-FC6H4)2P-(CH2)2-P-phi2]2 have been synthesized by the reaction of niobium(IV) chloride tetrahydrofuran adduct in THF with symmetrical and unsymmetrical ditertiary phosphines viz., 1,2-bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb), 1,5-bis(diphenylphosphino)pentane (dppent), 1,6-bis(diphenylphosphino)hexane (dpph), cis-1,2-bis(diphenylphosphino)ethylene (dppen) and 1-diphenylphosphino-2-bis[(p-fluoro)phosphino]ethane (dp(pf)pe). All these complexes have been characterized by elemental analyses, IR, H-1 NMR, P-31 NMR, C-13 NMR spectroscopy and magnetic susceptibility measurements.