Ancillary aryloxide ligands in ethylene polymerization catalyst precursors

The compounds CpTiCl2(OC6H3-i-Pr-2) (1), CpTiCl(OC6H3-i-Pr-2)(2) (2), CpTi( R)(OC6H3-i-Pr-2)(2) (R = t-Bu 3, s-Bu 4, n-Bu 5, Me 6) have been prepared a nd characterized. Compounds 1 or 2 in the presence of 500 equivalents of me thylaluminoxane (MAO) act as catalyst precursors for ethylene polymerizatio n. While the catalysts derived from the monocyclopentadienyl complexes are much less active that the metallocenes, there is a clear enhancement in the activity of about 40% as a result of the inclusion of a second aryloxide l igand. Reactions of 1 with AlMe3 revealed stepwise formation of CpTi(Me)Cl( OC6H3-i-Pr-2) 7 and CpTi(Me)(2)(OC6H3-i-Pr-2) 8, while subsequent addition of AlMe3 afforded complete conversion to 8, with formation of the aluminum species [AlMe2(OC6H3-i-Pr-2)](n) 9. In contrast, the catecholate complex Cp Ti(O2C6H4)Cl 10 reacts with AlMe3 yielding the paramagnetic species [CpTi(O -2(C6H4)). AlClMe2], 11. Incorporation of aryloxide ligands in modified met allocenes was readily accomplished with the preparation of Cp2ZrCl(OC6H3-i- Pr-2) 12, Cp2ZrCl(OC6H5) 13, Cp2ZrMe(OC6H5) 14 and Cp2TiCl(OC6H3-i-Pr-2) 15 . In combination with MAO, 12, 14 and 15 effect the polymerization of ethyl ene with an 11% increase in activity over the parent metallocenedichlorides . The implications of the increased activity are considered. Crystallograph ic data are reported for 2, 3, 6, 9, 11, 12 and 13. (C) 1999 Elsevier Scien ce S.A. All rights reserved.