Chiral titanium(IV) and vanadium(V) salen complexes as catalysts for carbon dioxide and epoxide coupling reactions

Recent Advancements in Metal‐catalysts Design for CO2/Epoxide Reactions

“…Titanium(IV) 3 (forming a bimetallic μ ‐oxo bridged structure in the solid state) and Vanadium(V) 4 complexes have been also reported by North and coworkers to catalyze the conversion of styrene oxide (SO) to styrene carbonate (SC) under a wide‐range of reaction conditions (0.1–5 MPa; 25–100 °C, 3–24 h) reaching a conversion of 98% conversion in 24 h by activation with TBAB (Figure 2). [45] Other terminal epoxides have been also converted to cyclic carbonates in good yields, while CHO only gives the corresponding cis ‐cyclohexene carbonate ( cis ‐CHC) in low yields (23–32% with the titanium and vanadium catalysts respectively). Notably, despite both the metal complexes are chiral, SO is converted in the corresponding carbonate in the racemic form.…”

Oxovanadium(V) catalysts for the CO2 fixation into cyclic carbonates under ambient pressure

“…[ 20 ] However, several mononuclear salen complexes were demonstrated to be not effective catalysts under mild reaction conditions. As compared to the comprehensive studies on salen catalysts, [ 21 ] the employment of non‐salen vanadium catalysts is still relatively unexplored. [ 22 ] Recently, the oxovanadium complex chelated with O 3 N‐aminotriphenolate ligand [ 23 ] has been demonstrated to stabilize high oxidation state V(V) center as a strong Lewis acid site for epoxide activation and exert the efficient coupling interactions via the cooperation of vanadium(V) center and coordinated phenolate‐O atom [ 24 ] Although the remarkable success of oxovanadium(V) complexes, chelated with aminotriphenolate ligand, on facilitating the coupling reactions between CO 2 and epoxide derivatives, the synthesis of the aminotriphenolate ligand requires multi‐step procedures which might limit its industrial applications.…”