The reaction between trisdiolatotungsten(VI) complex [W(eg)(3)] (1) (eg = 1,2-ethanediolato dianion) and phenolic ligand precursor methylamino-NN-bis(2-methylene-4,6-dimethylphenol) (H2LMe) or methylamino-NN-bis(2-methylene-4-methyl-6-tert-butylphenol) (H2LtBu) affords monomeric oxotungsten complex [WO(eg)(L-me)] (2) or [WO(eg)(L-tBu)] (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(L-Me)] (4) and [WOCl2(L-tBu)] (5), respectively. Identical dichlorc, 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.