Efficient CO2 fixation into cyclic carbonates catalyzed by NNO-scorpionate zinc complexes

Abstract

A series of new chiral zwitterionic NNO-scorpionate mononuclear zinc alkyls [Zn(R)(κ³-NNO)]Br was developed in very high yields via suitable quaternization in the scorpionate ligand. These zwitterionic complexes performed as bifunctional catalysts and exhibited improved catalytic activity for the fixation of CO₂ into cyclic carbonates compared to the neutral analog mononuclear [Zn(R)(κ³-NNO)] and binuclear [Zn(R)(κ²-NNμ-O)Zn(R)₂] compounds. The catalyst system showed a broad substrate scope and functional group tolerance under mild and solvent-free conditions.