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Synthesis of Half-Titanocenes Containing Anionic N-Heterocyclic Carbenes That Contain a Weakly Coordinating Borate Moiety, Cp′TiX 2 (WCA-NHC), and Their Use as Catalysts for Ethylene (Co)polymerization

2019; American Chemical Society; Volume: 38; Issue: 17 Linguagem: Inglês

10.1021/acs.organomet.8b00841

1520-6041

Kotohiro Nomura, Go Nagai, Alexandre Nasr, Ken Tsutsumi, Yuta Kawamoto, Koji Koide, Matthias Tamm,

Synthetic Organic Chemistry Methods

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.