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NNC-Scorpionate Zirconium-Based Bicomponent Systems for the Efficient CO 2 Fixation into a Variety of Cyclic Carbonates

2020; American Chemical Society; Volume: 59; Issue: 17 Linguagem: Inglês

10.1021/acs.inorgchem.0c01532

1520-510X

Juan Fernández‐Baeza, Luis F. Sánchez‐Barba, Agustín Lara‐Sánchez, Sonia Sobrino, Jaime Martínez‐Ferrer, Andrés Garcés, Marta Navarro, Ana M. Rodrı́guez,

Chemical Synthesis and Reactions

Two new derivatives of the bis(3,5-dimethylpyrazol-1-yl)methane modified by introduction of organosilyl groups on the central carbon atom, one of which bearing a chiral fragment, have been easily prepared. We verified the potential utility of these compounds through the reaction with [Zr(NMe2)4] for the preparation of novel zirconium complexes in which an ancillary bis(pyrazol-1-yl)methanide acts as a robust monoanionic tridentate scorpionate in a κ3-NNC chelating mode, forming strained four-membered heterometallacycles. These κ3-NNC-scorpionate zirconium amides were investigated as catalysts in combination with tetra-n-butylammonium bromide as cocatalyst for CO2 fixation into five-membered cyclic carbonate products. The study has led to the development of an efficient zirconium-based bicomponent system for the selective cycloaddition reaction of CO2 with epoxides. Kinetics investigations confirmed apparent first-order dependence on the catalyst and cocatalyst concentrations. In addition, this system displays very broad substrate scope, including mono- and disubstituted substrates, as well as the challenging biorenewable terpene derived limonene oxide, under mild and solvent-free conditions.