Easily Available Niobium(V) Mixed Chloro-Alkoxide Complexes as Catalytic Precursors for Ethylene Polymerization

The dinuclear [NbCln(OR)(5-n)]2 complexes (n = 4, R = Et, 1; n = 4, R = CH2Ph, 2; n = 3, R = Et, 3; n = 2, R = Et, 4; n = 2, R = , 5), and [Nb(OEt)5]2, 6, and the mononuclear Nb compds. NbCl4[.kappa.2-OCH2CH(R')OR] (R = Me, R' = H, 7; R = Et, R' = H, 8; R = CH2Cl, R' = H, 9; R = CH2CH2OMe, R' = H, 10; R = R' = Me, 11), NbBr4[.kappa.2-OCH2CH2OMe], 12, and NbCl3(.kappa.2-OCH2CH2OMe)(.kappa.1-OCH2CH2OMe), 13, were tested in ethylene polymn. Optimized reaction conditions included the use of D-MAO as co-catalyst and chlorobenzene as solvent at 50. Complex 7, whose x-ray structure is described here for the first time, exhibited the highest activity ever reported for a Nb catalyst in alkene polymn. [151 kg polymer molNb-1 h-1 bar-1]. Compds. 1, 3-5, 8, 13 showed activities similar to that of 7. Linear polyethylenes (characterized by FTIR, NMR, GPC, and DSC analyses) with a broad polydispersivity were obtained.