Acetato complexes of molybdenum(V): A novel tetranuclear core based on the metal–metal bonded {Mo2O4}2+ units

A series of acetato complexes of molybdenum(V), based on the singly metal–metal bonded {Mo2O4}2+ structural fragment, has been prepared. A dinuclear (PyH)3[Mo2O4Cl4(OOCCH3)] · CH3CN (1) (PyH+ = pyridinium cation, C5H5NH+) was obtained upon the reaction of (PyH)5[MoOCl4(H2O)]3Cl2 with the equimolar solution of pyridine and acetic acid in acetonitrile at ambient conditions. The acetato ligand in 1 is coordinated to a pair of molybdenum atoms in a syn–syn bidentate bridging manner. (PyH)n[MoOBr4]n afforded in an analogous synthetic procedure a tetranuclear cluster, [Mo4O8(OOCCH3)3(OH)Py4] · 1/2CH 3CN · 1/2H2O (3), with a novel core which may be envisioned as the acetate- and hydroxide-assisted assembly of {Mo2O4}2+ building blocks. Its structure is presented in terms of known tetranuclear clusters which are also composed of two {Mo2O4}2+ units. The acetato ligands in 3 adopted apart from bidentate bridging binding modes also a monodentate one. Partial substitution of chlorido ligands in (PyH)3[Mo2O4Cl4(OOCCH3)] · CH3CN (1) with pyridine resulted in a neutral [Mo2O4Cl(OOCCH3)Py3] · PriOH · Py (2) which retained the original acetate coordination. The title compounds were fully characterized by X-ray diffraction studies and infrared vibrational spectroscopy.