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)] center dot CH3CN (1) (PyH+ = pyridinium cation, C5H5NH+) was obtained upon the reaction of (PyH)(5)[MoOCl4(H2O)](3)Cl-2 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)Py-4] center dot 1/2CH 3CN center dot 1/2H(2)O(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)] center dot CH3CN (1) with pyridine resulted in a neutral [Mo2O4Cl(OOCCH3)Py-3] center dot (PrOH)-O-i center dot Py (2) which retained the original acetate coordination. The title compounds were fully characterized by X-ray diffraction studies and infrared vibrational spectroscopy. (c) 2008 Elsevier B. V. All rights reserved.