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Issue 12, 2013
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The reductive disproportionation of CO2 using a magnesium(I) complex: analogies with low valent f-block chemistry

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Abstract

The dimeric magnesium(I) complex, [{(DipNacnac)Mg}2] (DipNacnac = [(DipNCMe)2CH], Dip = C6H3Pri2-2,6), reacts with 2 equivalents of CO2 to give a high yield of the MgII carbonate complex, [{(DipNacnac)Mg}2(μ-κ22-CO3)], and CO via a reductive disproportionation process. The MgII oxalate, [{(DipNacnac)Mg}2(μ-C2O4)], is a very low yield by-product of the reaction. Reducing the carbonate complex with elemental potassium regenerates the MgI starting material. The carbonate complex is shown to form via a stepwise process involving the oxo-bridged intermediate, [{(DipNacnac)Mg}2(μ-O)], which rapidly reacts with stoichiometric CO2 to give [{(DipNacnac)Mg}2(μ-κ22-CO3)]. The oxo-bridged intermediate has been rationally synthesised via the reaction of [{(DipNacnac)Mg}2] with N2O, and treated with THF to give the adduct, [{(THF)(DipNacnac)Mg}2(μ-O)]. The complex, [{(DipNacnac)Mg}2(μ-O)], reacts with the CO2 isoelectronic analogues, CS2 and CyNCNCy (Cy = cyclohexyl) to give the complexes, [{(DipNacnac)Mg}2(μ-κ22-CS2O)] and [{(DipNacnac)Mg}2{μ-κ22-C(NCy)2O}]. Rearrangement of the dithiocarbonate coordination mode of the former occurs upon treatment with diethyl ether, giving the unsymmetrical complex, [{(DipNacnac)Mg}(μ-κ2(S,S′):κ1(O)-CS2O){Mg(DipNacnac)(OEt2)}]. The majority of the complexes prepared in this study were crystallographically characterised. Taken as a whole, this study demonstrates that magnesium(I) dimers can display very similar reactivity, with respect to small molecules activations, as do SmII and UIII compounds. Accordingly, magnesium(I) compounds hold considerable potential as cheaper, less toxic, non-radioactive and diamagnetic alternatives to low valent f-block metal complexes in this realm.

Graphical abstract: The reductive disproportionation of CO2 using a magnesium(i) complex: analogies with low valent f-block chemistry

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Publication details

The article was received on 10 Aug 2013, accepted on 30 Aug 2013 and first published on 30 Aug 2013


Article type: Edge Article
DOI: 10.1039/C3SC52242C
Citation: Chem. Sci., 2013,4, 4383-4388
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    The reductive disproportionation of CO2 using a magnesium(I) complex: analogies with low valent f-block chemistry

    R. Lalrempuia, A. Stasch and C. Jones, Chem. Sci., 2013, 4, 4383
    DOI: 10.1039/C3SC52242C

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