With a new titanium imineenolato complex, ethylene is polymerized in an unprecedented living fashion affording a polymer with a high molecular weight (M n > 105 g mol−1) and an extremely narrow distribution (M w/M n 1.01) at the same time; the living character is also retained even at an elevated temperature of 75 °C, and blockcopolymers are accessible.

Water-soluble complexes based on enolatoimine ligands bearing electron-withdrawing trifluoromethyl groups) TPPTS with TPPDS ) PhP(p-C 6 H 4 SO 3 Na) 2 and TPPTS ) P(m-C 6 H 4 SO 3 Na) 3 ) were prepared. These complexes polymerize ethylene to very small (10-30 nm) semicrystalline particles of high molecular weight (up to M w 1.6 × 10 6 g mol -1 ) polymer with a degree of branching (7-63 branches per 1000 C atoms) and thus crystallinity (e25-50%) and melt transition temperatures (T m ) 75-129 °C) variable over a large range, depending on the substituents of the N-aryl moiety (2,6-R 2 C 6 H 3 ), and the polymerization temperature. The catalysts are stable for hours under polymerization conditions (50 °C) in the highly disperse aqueous system.

A series of new, electron-poor neutral κ 2 -N,O chelated Ni(II) complexes were studied for ethylene polymerization in aqueous emulsion. Complexes based on enolatoimine ligands bearing electron-withdrawing trifluoromethyl and trifluoroacetyl groups [κ2-N,O-{2,6-R2C6H3NC(H)C(COCF3)C(O)CF3}]Ni(L)Me (4a, R = iPr, L = pyridine; 4b, R = 3,5-(CF3)2C6H3, L = pyridine; 5b, R = 3,5-(CF3)2C6H3, L = PPh3) were prepared. The complexes are very active in aqueous emulsions, with 1.4 × 104 TO h-1 for 4a (50 °C) and 1.9 × 104 TO h-1 for 4b (70 °C), affording stable polyethylene dispersions. The phosphine complex 5b is active in the absence of a phosphine scavenger, with similar activities as 4b. Polyethylenes of typically M w 3 × 104 g mol-1 (M w/M n 2.0−2.5) with 25−50 branches per 1000 carbon atoms and T m 94−112 °C are obtained.

Zirconium complexes with enolatoimine ligands bearing an electron-withdrawing trifluoromethyl group on the alkoxy moiety [κ²-N,O-{2,6-R₂N=C(CH₃)C(H)=C(O)CF₃]₂ZrCl₂ (2a, R = H; 2b, R = F; 2c, R = CH₃; 2d, R = (i)Pr) were prepared. The isopropyl substituents hinder rotation in solution for 2d, and result in a trans-arrangement of the N-donors in the solid state. Catalyst activities are similar for 2a/MAO and 2b/MAO in ethylene polymerization (1.8 × 10⁵ TO h⁻¹ for 2a and 3.3 × 10⁵ TO h⁻¹ for 2b at 25 °C under 1 bar monomer pressure), increasingly bulky alkyl substituents result in strongly decreased polymerization activities (7.1 × 10² TO h⁻¹ for 2c and 5.7 × 10² TO h⁻¹ for 2d at 25 °C). This goes along with an increase in polymer molecular weight (M(w) = 8.1 × 10³, M(w)/M(n) = 2.9 for 2a, M(w) = 3.8 × 10⁵, M(w)/M(n) = 2.0 for 2b, M(w) = 1.0 × 10⁶, M(w)/M(n) = 2.8 for 2c), apparently bulky substituents retard chain transfer even more strongly than activation of the precursors and/or chain growth. 2b/MAO affords atactic polypropylene (M(w) = 1.4 × 10⁴ g mol⁻¹, M(w)/M(n) = 2.1) with a small portion of regioirregular structures. The reaction of [Zr(CH₂Ph)₄] with the ketoenamine 2,6-F₂C₆H₃N(H)-CMe=CHC(O)CF₃ (1b) yielded the dibenzyl complex [(o-F₂C₆H₃N=CMeCH=C(CF₃)O)₂Zr-(CH₂Ph)₂] (3b) which was investigated as a catalyst precursor for ethylene homopolymerization in combination with different activators.

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