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Issue 41, 2016
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Tri-, tetra-, and hexanuclear mixed-valence molybdenum clusters: structural diversity and catalysis of acetylene hydrogenation

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Abstract

A series of novel cluster compounds comprising molybdenum in a low valence state was synthesized by means of a disproportionation of the dimeric compound [Mo+42Cl4(OCH3)4(CH3OH)2] (1). The reaction of 1 with CH3OH leads to the disproportionation of Mo+4 yielding an unusual mixed-valence cluster [Mo+3.54Cl4O2(OCH3)6(CH3OH)4] (2). By exploring this synthetic approach further, tri-{[Mo3Cl3(OCH3)7(CH3OH)3] (3)}, tetra-{[Mo4Cl4(OCH3)10(CH3OH)2] (4), [Mo4Cl3O(OCH3)9(CH3OH)3] (5), [Mo4Cl2(OCH3)12(CH3OH)2] (6)}, and hexanuclear {[Mo6Cl4O6(OCH3)10(CH3OH)2] (7)} molybdenum alkoxides were synthesized by the reaction of 1 with methanol and stoichiometric amounts of magnesium methoxide, thus providing a general facile access to the polynuclear methoxide complexes of a low-valence molybdenum. Due to the feasibility to adopt multiple oxidation states in a reversible manner and the documented competence of molybdenum alkoxide compounds to catalyze the reduction of inert molecules, including N2, the synthesized compounds were expected to function as catalysts of small molecule substrates reduction/hydrogenation. Accordingly, the reduction of acetylene (C2H2) to an ethylene (C2H4) and ethane (C2H6) mixture, in methanol (with water additives) serving as a reaction medium and a proton donor, and using sodium or europium amalgams as reducing agents, was performed in the presence of 2. Preliminary kinetic studies evidently point to a catalytic function of molybdenum species derived from 2, thus establishing the observed reactivity as a rare example of non-precious metal-catalyzed acetylene hydrogenation, providing, in addition, a convenient model for further mechanistic studies.

Graphical abstract: Tri-, tetra-, and hexanuclear mixed-valence molybdenum clusters: structural diversity and catalysis of acetylene hydrogenation

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Publication details

The article was received on 27 Jul 2016, accepted on 07 Sep 2016 and first published on 08 Sep 2016


Article type: Paper
DOI: 10.1039/C6DT02965E
Dalton Trans., 2016,45, 16309-16316

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    Tri-, tetra-, and hexanuclear mixed-valence molybdenum clusters: structural diversity and catalysis of acetylene hydrogenation

    D. A. Kuznetsov, T. A. Bazhenova, I. V. Fedyanin, V. M. Martynenko, A. F. Shestakov, G. N. Petrova and N. S. Komarova, Dalton Trans., 2016, 45, 16309
    DOI: 10.1039/C6DT02965E

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