Synthesis of Half-Titanocenes Containing Anionic N‑Heterocyclic Carbenes That Contain a Weakly Coordinating Borate Moiety, Cp′TiX2(WCA-NHC), and Their Use as Catalysts for Ethylene (Co)polymerization

Synthesis and structural analysis of half-titanocenes containing anionic N-heterocyclic carbenes with a weakly coordinating borate [B­(C6F5)3] moiety (WCA-NHC) of the type, [Cp′TiX2(WCA-NHC)] [Cp′ = C5H5, tBuC5H4; X = Cl, Me; NHC = 1,3-bis­(2,6-dimethylphenyl)­imidazolin-2-ylidene], have been explored. The Ti–C bond distances between titanium and the N-heterocyclic carbene carbon atoms [Ti–CNHC = 2.214(3)–2.246(3) Å] are longer than the Ti–methyl bond distances in the dimethyl complexes [2.063(5)–2.122(9) Å]; the WCA-NHC ligand coordinates to titanium as a conventional N-heterocyclic carbene ligand. [(tBuC5H4)­TiCl2(WCA-NHC)] exhibited high catalytic activity (e.g., 4590 kg-PE/mol-Ti·h) for ethylene polymerization in the presence of AliBu3–[Ph3C]­[B­(C6F5)4] cocatalyst, and the complex demonstrated high catalytic activity with efficient 1-hexene incorporation for the ethylene/1-hexene copolymerization in the presence of MAO cocatalyst.