New publication

Reduction of carbon dioxide and organic carbonyls by hydrosilanes catalysed by the perrhenate anion

Danny S. Morris, Catherine Weetman, Julian T. C. Wennmacher, Mirza Cokoja, Markus Drees, Fritz E. Kühn, and Jason B. Love, Catal. Sci. Technol., 2017

ToC CatSciTechnol

The simple perrhenate salt [N(hexyl)4][(ReO4)] acts as a catalyst for the reduction of organic carbonyls and carbon dioxide by primary and secondary hydrosilanes. In the case of CO2, this results in the formation of methanol equivalents via silylformate and silylacetal intermediates. Furthermore, the addition of alkylamines to the reaction mixture favours catalytic amine N-methylation over methanol production under certain conditions. DFT analysis of the mechanism of CO2 reduction shows that the perrhenate anion activates the silylhydride forming a hypervalent silicate transition state such that the CO2 can directly cleave a Si-H bond.

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New publication

“Triggering redox activity in a thiophene compound: radical stabilization and coordination chemistry”

M. Curcio, J. R. Pankhurst, S. Sproules, D. Mignard, J. B. Love, Angew. Chem. Int. Ed.2017, DOI: 10.1002/anie.201703576R1

thiophene

Abstract: The synthesis, metalation, and redox properties of an acyclic bis(iminothienyl)methene L are presented. This π-conjugated anion displays pronounced redox activity, undergoing facile one-electron oxidation to the acyclic, metal-free, neutral radical L on reaction with FeBr2. In contrast, reaction of L with CuI forms the unique, neutral Cu2I2(L) complex of a ligand-centered radical, whereas reaction with the stronger oxidant AgBF4 forms the metal-free radical dication L2+.

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New publication

Multi-electron reduction of sulfur and carbon disulfide using binuclear uranium(III) borohydride complexes

Polly L. Arnold,* Charlotte J. Stevens, Nicola L. Bell, Rianne M. Lord, Jonathan M. Goldberg, Gary S. Nichol and Jason B. Love* Chem. Sci. 2017, DOI: 10.1039/c7sc00382j

chemsci2017

The first use of a dinuclear UIII/UIII complex in the activation of small molecules is reported. The octadentate Schiff-base pyrrole, anthracene-hinged ‘Pacman’ ligand LA combines two strongly reducing UIII centres and three borohydride ligands in [M(THF)4][{U(BH4)}2(µ-BH4)(LA)(THF)2] 1-M, (M = Li, Na, K). The two borohydride ligands bound to uranium outside the macrocyclic cleft are readily substituted by aryloxide ligands, resulting in a single, weakly-bound, encapsulated endo potassium borohydride bridging the two UIII centres in [{U(OAr)}2(m-MBH4)(LA)(THF)2] 2-M (OAr = OC6H2tBu3-2,4,6, M = Na, K). X-ray crystallographic analysis shows that, for 2-K, in addition to the endo-BH4 ligand the potassium counter-cation is also incorporated into the cleft through η5-interactions with the pyrrolides instead of extraneous donor solvent. As such, 2-K has a significantly higher solubility in non-polar solvents and a wider U-U separation compared to the ‘ate’ complex 1. The cooperative reducing capability of the two UIII centres now enforced by the large and relatively flexible macrocycle is compared for the two complexes, recognising that the borohydrides can provide additional reducing capability, and that the aryloxide-capped 2-K is constrained to reactions within the cleft. The reaction between 1-Na and S8 affords an insoluble, presumably polymeric paramagnetic complex with bridging uranium sulfides, while that with CS2 results in oxidation of each UIII to the notably high UV oxidation state, forming the unusual trithiocarbonate (CS3)2- as a ligand in [{U(CS3)}2(m-k1:k1:h2-CS3)(LA)] (4). The reaction between 2-K and S8 results in quantitative substitution of the endo-KBH4 by a bridging persulfido (S2)2- group and oxidation of each UIII to UIV, yielding [{U(OAr)}2(μ-h2:h2-S2)(LA)] (5). The reaction of 2-K with CS2 affords a thermally unstable adduct which is tentatively assigned as containing a carbon disulfido (CS2)2- ligand bridging the two U centres (6a), but only the mono-bridged sulfido (S)2- complex [{U(OAr)}2(μ-S)(LA)] (6) is isolated. The persulfido complex (5) can also be synthesised from the mono-bridged sulfido complex (6) by the addition of another equivalent of sulfur.

 

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Welcome to Daniel

Daniel Henschel from the Technical University of Munich has joined the group for the next 6 months to carry out his Master’s thesis project on sulfur analogues of dipyrrin complexes for small molecule activation.

p1000198

 

 

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Metal recovery in Chile

Mary Healy, Carole Morrison, and Jason love have just returned from Chile where they were hosted by Alvaro Videla and Rene Rojas of the Pontifical University of Chile in Santiago. Lots of great interactions with academics and industrialists, plus visits to mines, recovery plants, and the Atacama desert!

Shown here is a copper solvent extraction plant (Amalia Catemu) where we saw the whole recovery process for copper, and the Andes in the Atacama desert, the location of Chuquicamata, one of the largest copper mines in the world.

mixer-settlerandes_2017

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Urban mining

An episode of BBC Scotland’s ‘Brainwaves’ science programme discussing urban mining with contributions from the Edinburgh Metal Recovery Group is available for download

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Government 20

An overview of some of the work carried out by the Metal Recovery Group at Edinburgh is provided in the Pan European Network “Government 20” publication (Page 154).

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