Dioxomolybdenum(VI) complex [MoO 2Cl 2(dmso) 2] reacts with a series of tetradentate O 3N-type aminoalcohol–bisphenol ligands to form oxomolybdenum(VI) complexes of type [MoOCl(L n )]. The reaction of H 3L 1 produces [MoOCl(L 1)] as two separable isomers, whereas the reaction of H 3L 2 or H 3L 3 yields a single product. The X-ray analyses of cis- and trans-[MoOCl(L 1)] reveal that the complexes are formed of monomeric molecules. The ligands have tetradentate coordination through three oxygen donors and one nitrogen donor, which is located trans to the terminal oxo group. The sixth coordination site is occupied by a chloro ligand.