Easily Accessible Oxygen-Containing Derivatives of Niobium Pentachloride as Catalytic Precursors for Ethylene Polymerization

The low catalytic activity of NbCl5 as an ethylene polymn. catalyst was significantly increased by the addn. of a series of oxygen donors. The novel niobium derivs. NbCl5(OPh2) (1), NbCl5(OEt2) (3), NbCl5(O[n.63742]CPh2) (5), NbCl5(O[n.63742]CHPh) (6), NbCl5(O[n.63742]CHMe) (7) and [NbCl4(dppe)2](NbCl6) (18) (dppe is 1,2-bis(diphenylphosphino)ethane) and the previously reported derivs. NbCl5(OMePh) (2), NbCl5(thf) (4) (thf is tetrahydrofuran), NbCl5(O[n.63742]CHOMe) (8), NbCl5(O[n.63742]CHNMe2) (9), NbCl5[O[n.63742]C(NMe2)2] (10), NbCl5(NCMe) (11), NbCl4(.kappa.2-1,2-OC6H4OMe) (12), NbCl4[.kappa.2-O[n.63742]C(Me)CH2C(Me2)O] (13), (14), [NbCl4(O2CMe)]2 (15), NbCl3(dme)(.mu.-O)NbCl5 (16) (dme is 1,2-dimethoxyethane), [NbCl4(.kappa.2-dmm)2](NbCl6) (17) (dmm is dimethylmaleate), TaCl5(O[n.63742]CMe2) (19) and [TaCl4(O2CMe)]2 (20) were tested as catalytic precursors in the ethylene polymn. reaction using AlMe3-depleted methylaluminoxane as co-catalyst. Highly linear polyethylene was obtained. Compds. 1, 3, 5, 6 and 8-13 showed catalytic activities in the range 89-116 kgpolymer molNb-1 h-1 bar-1, i.e. comparable with the best performances reached with niobium pre-catalysts up to now. However, the dinuclear compds. 14-16 and 18 were found to be less active, whereas17 and the tantalum derivs. 19 and 20 did not produce polymer. Relatively high mol. wts. were achieved with the mononuclear compds. 1, 2, 8, 9, 10 and 12, the dinuclear 16 and the phosphine ionic 18. Copyright 2011 Society of Chem. Industry.