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Reversible complexation of ammonia by breaking a manganese–manganese bond in a manganese carbonyl ethylenedithiolate complex: a theoretical study of an unusual type of Lewis acid

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Abstract

The reaction of Mn(CO)5Br with sodium ethylenedithiolate was reported in 1968 to give a dark red binuclear H2C2S2Mn2(CO)6 complex possessing the unusual property of complexing reversibly with ammonia to give a yellow H2C2S2Mn2(CO)6·NH3 adduct. In order to provide some insight into the nature of this adduct, density functional studies were performed on the H2C2S2Mn2(CO)n (n = 4 to 8) systems as well as their relevant ammonia and trimethylphosphine adducts. These theoretical studies support the structure of H2C2S2Mn2(CO)6 originally suggested 50 years ago involving the binding of the ethylenedithiolate C[double bond, length as m-dash]C double bond as well as the sulfur atoms to the Mn2 unit with a bonding Mn–Mn distance of ∼2.8 Å. Complexation of H2C2S2Mn2(CO)6 with NH3 or Me3P preserves the complexed C[double bond, length as m-dash]C double bond of the ethylenedithiolate ligand but lengthens the Mn⋯Mn distance to a non-bonding ∼3.6 Å. Thus H2C2S2Mn2(CO)6 represents a novel type of Lewis acid where reversible complexation with Lewis bases involves the rupture of a metal–metal bond. Carbonyl dissociation energies in the H2C2S2Mn2(CO)n series account for the formation of the hexacarbonyl H2C2S2Mn2(CO)6 as the stable product from the Mn(CO)5Br/ethylenedithiolate reaction.

Graphical abstract: Reversible complexation of ammonia by breaking a manganese–manganese bond in a manganese carbonyl ethylenedithiolate complex: a theoretical study of an unusual type of Lewis acid

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Publication details

The article was received on 22 Oct 2018, accepted on 11 Nov 2018 and first published on 20 Nov 2018


Article type: Paper
DOI: 10.1039/C8DT04217A
Citation: Dalton Trans., 2019, Advance Article
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    Reversible complexation of ammonia by breaking a manganese–manganese bond in a manganese carbonyl ethylenedithiolate complex: a theoretical study of an unusual type of Lewis acid

    L. Radu, A. A. A. Attia, R. Silaghi-Dumitrescu, A. Lupan and R. B. King, Dalton Trans., 2019, Advance Article , DOI: 10.1039/C8DT04217A

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