Abstract
Two novel heteropolyoxomolybdate [XMo8O31]n− (X = Ge(1) or P(2)) manganese carbonyl derivatives [(CH3)4N]6H6{MnII(GeMo8O31)[MnI(CO)3]2}2·12H2O (1) and [(CH3)4N]4H6{MnII(PMo8O31)[MnI(CO)3]2}2·14H2O (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 {Mn2(XMo8O31)2}n− through MnI-O-Mo bonds. The carbonyl functionalized Mn atoms are octahedrally coordinated via three μ2-oxygens of the [XMo8O31]n− unit and three carbonyl carbon atoms. Interestingly, 1 and 2 form a psedocuboidal ring Mn(CO)3Mo3O12 with {Mn(CO)3}+ occupying the three fold axis of the Mo3O12 octahedral triad. Beside this, the two centrally placed adjacent MnII 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.
Highlights
Polyoxometalates (POMs), are a unique class of metal-oxo clusters, widely studied in different scientific fields such as catalysis, magnetism, medicine and functional materials due to their versatile structures and efficient properties [1,2,3,4,5,6,7,8]
Since the advent of the first POM-incorporating carbonyl cobalt derivative reported by Knoth in 1979 [18], POM-based metal carbonyl derivatives have emerged as compounds of significant importance and are being increasingly studied
All non-hydrogen atoms were refined anisotropically except for some water molecules. In this contribution we have reported the syntheses and structure elucidation of two new heteropolyoxomolybdate-supported tetracarbonyl metal derivatives 1 and 2 by conventional methods
Summary
Polyoxometalates (POMs), are a unique class of metal-oxo clusters, widely studied in different scientific fields such as catalysis, magnetism, medicine and functional materials due to their versatile structures and efficient properties [1,2,3,4,5,6,7,8]. Metal carbonyl-functionalized POMs have emerged as an important category of organometallic hybrid clusters that mainly attract attention due to their role in providing new structural classes by altering the electronic and structural features of the basic transition metal-substituted POMs structural motifs [12,13]. Since the advent of the first POM-incorporating carbonyl cobalt derivative reported by Knoth in 1979 [18], POM-based metal carbonyl derivatives have emerged as compounds of significant importance and are being increasingly studied. Transition metal sandwiched heteropolyoxomolybdates incorporating metal cartbonyl units are still very few In this context, and our interest in exploring and developing organometallic-based POM clusters, encouraged us to successfully obtain two new tetravacant Keggin-type heteropolyoxomolybdate metal carbonyl derivatives:. The detailed studies related to their synthesis, and interesting redox behaviour due to active MnII /MnI redox couple, were undertaken and the results of these investigations are described here
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