Reductive Hexamerization of CO Involving Cooperativity Between Magnesium(I) Reductants and [Mo(CO)6]: Synthesis of Well‐Defined Magnesium Benzenehexolate Complexes

• Published in: Angewandte Chemie International Edition 2021-01, Vol.60 (2), p.630-634
• Main Authors: Paparo, Albert, Yuvaraj, K., Matthews, Aidan J. R., Douair, Iskander, Maron, Laurent, Jones, Cameron
• Format: Article
• Language: English
• Subjects: benzenehexolate; Carbon monoxide; Chemical Physics; Chemical reactions; DFT calculations; Fischer-Tropsch process; homologation; Magnesium; Physics; Potassium; Reducing agents
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202009523

Reactions of two magnesium(I) compounds, [{(ArNacnac)Mg}2] (ArNacnac=[HC(MeCNAr)2]−; Ar=mesityl (Mes) or o‐xylyl (Xyl)), with CO in the presence of [Mo(CO)6] lead to the reductive hexamerization of CO, and formation of magnesium benzenehexolate complexes, [{(ArNacnac)Mg}6(C6O6)]. [Mo(CO)6] is not consumed in these reactions, but is apparently required to initiate (or catalyze) the CO hexamerizations. A range of studies were used to probe the mechanism of formation of the benzenehexolate complexes. The magnesium(I) reductive hexamerizations of CO are closely related to Liebig's reduction of CO with molten potassium (to give K6C6O6, amongst other products), originally reported in 1834. As the mechanism of that reaction is still unknown, it seems reasonable that magnesium(I) reductions of CO could prove useful homogeneous models for its elucidation, and for the study of other C−C bond forming reactions that use CO as a C1 feedstock (e.g. the Fischer–Tropsch process). Magnesium benzenehexolate complexes are prepared by reductive hexamerizations of CO, in reactions that are initiated (or catalyzed) by [Mo(CO)6]. These reactions are closely related to Justus von Liebig's classical 1834 study on the reduction of CO gas with molten potassium, which yields K6C6O6 (amongst other products), by an as‐yet unknown mechanism.