Tungsten(VI) Complexes with Aminobis(phenolato) [O,N,O] Donor Ligands

The reaction between trisdiolatotungsten(VI) complex [W(eg)3] (1) (eg = 1,2-ethanediolato dianion) and phenolic
ligand precursor methylamino-N,N-bis(2-methylene-4,6-dimethylphenol) (H2LMe) or methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol) (H2LtBu) affords monomeric oxotungsten complex [WO(eg)(LMe)] (2) or [WO(eg)(LtBu)]
(3), respectively. These complexes react further with chlorinating reagents, which leads to the displacement of
ethanediolato ligands from the complex units and formation of cis and trans isomers of the corresponding dichloro
complexes [WOCl2(LMe)] (4) and [WOCl2(LtBu)] (5), respectively. Identical dichloro complexes were also prepared
by the reaction between the above-mentioned phenolic ligand precursors and [WOCl4]. Molecular structures of 3,
cis-4, trans-4, and cis-5 were verified by X-ray crystallography. Complexes 2−5 can be activated by Et2AlCl to
catalyze ring-opening metathesis polymerization of norbornene.