Mechanism of the catalytic carboxylation of alkylboronates with CO2 using Ni-NHC complexes : a DFT study
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A new mechanism is proposed for the Ni-catalysed carboxylation of organoboronates with CO2. DFT investigations at the PBE0-D3 level have shown that direct CO2 addition to the catalysts [Ni(NHC)(Allyl)Cl] (1NHC, NHC = IMe, IPr, SIPr and IPr*) is kinetically disfavored and formation of the Aresta-type intermediate is unlikely to occur. According to the mechanism proposed here, the carboxylation process starts with addition of the borate species to 1NHC, followed by transmetalation, CO2 cycloaddition and carboxylation. The rate-determining step was identified as being the transmetalation process, with computed relative free energy barriers of 34.8, 36.8 and 33.5 kcal mol-1 for 1IPr, 1SIPr and 1IPr*, respectively
Delarmelina , M , Marelli , E , Carneiro , J , Nolan , S & Buehl , M 2017 , ' Mechanism of the catalytic carboxylation of alkylboronates with CO 2 using Ni-NHC complexes : a DFT study ' , Chemistry - A European Journal , vol. 23 , no. 59 , pp. 14954-14961 . https://doi.org/10.1002/chem.201703567
Chemistry - A European Journal
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This work has been made available online in accordance with the publisher’s policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at: https://doi.org/10.1002/chem.201703567
DescriptionThe authors acknowledge FAPERJ for providing research grants and financial support. MB thanks the School of Chemistry and EaStCHEM for support and for access to a computer cluster maintained by Dr H. Früchtl. JWMC acknowledges CNPq for a research grant. The experimental work was supported via our membership of the UK Catalysis Hub consortium funded by EPSRC (grants EP/K014706/2, EP/K014668/1, EP/K014854/1 and EP/K014714/1). SPN gratefully acknowledges the European Commission for support in the form of an ERC Advanced Researcher grant (227817-FUNCAT).
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