Two New Tetravacant Organometallic Keggin-Type Heteropolyoxomolybdates-Supported Manganese Carbonyl Derivatives

Two novel heteropolyoxomolybdate [XMo(8)O(31)](n−) (X = Ge(1) or P(2)) manganese carbonyl derivatives [(CH(3))(4)N](6)H(6){Mn(II)(GeMo(8)O(31))[Mn(I)(CO)(3)](2)}(2)·12H(2)O (1) and [(CH(3))(4)N](4)H(6){Mn(II)(PMo(8)O(31))[Mn(I)(CO)(3)](2)}(2)·14H(2)O (2), have been successfully synthesized and characterized in the solid state by single crystal X-ray diffraction, IR and thermogravimetric analysis, and in solution by UV-Vis spectroscopy and electrochemistry. The two polyoxomolybdate-based organometallic compounds 1 and 2 represent rare examples of transition metal sandwich-based polyoxometalate metal carbonyl derivatives (PMCDs), in which the organic-inorganic hybrids are composed of four Mn(CO)(3)(+) groups symmetrically occupied the tetravacant sites of dimeric heteropolyoxomolybdate {Mn(2)(XMo(8)O(31))(2)}(n−) through Mn(I)-O-Mo bonds. The carbonyl functionalized Mn atoms are octahedrally coordinated via three μ(2)-oxygens of the [XMo(8)O(31)](n−) unit and three carbonyl carbon atoms. Interestingly, 1 and 2 form a psedocuboidal ring Mn(CO)(3)Mo(3)O(12) with {Mn(CO)(3)}(+) occupying the three fold axis of the Mo(3)O(12) octahedral triad. Beside this, the two centrally placed adjacent Mn(II) atoms show intramolecular Mn∙∙∙Mn interactions of 3.11 and 3.16 Å in 1 and 2, respectively. Significant n→π* and O···O intermolecular interactions between the orthogonally aligned adjacent carbonyl groups through the overlap of lone-pair electrons on oxygen atoms with the antibonding orbital (π*) of the adjacent carbony carbon atom of the subsequent units in 1 and 2 were observed. The electrochemical properties of the two compounds were also been investigated.