Hydroboration of CO2 catalyzed by heteroscorpionate zwitterionic zinc and magnesium hydride complexes

Abstract

The heteroscorpionate zinc hydride complex LZnH 2, (L = (MePz)₂CP(Ph)₂NPh, MePz = 3,5-dimethylpyrazolyl), its formate complex 3, and magnesium hydride complex LMgH 5 with the same ligand were synthesized and detected for the catalytic hydroboration reaction of CO₂. With BH₃·SMe₂ as the reductant, zinc-based hydride complex 2 and formate complex 3 show a similar capability of hydroboration of CO₂, featuring excellent reactivity and selectivity. The conversion of BH₃·SMe₂ reached 84%, the highest TON of 252 compared to other zinc catalysts was achieved at room temperature and borate ester products at reduction levels of CH₃OH were obtained. Magnesium-based hydride complex 5 showed inferior activity for the hydroboration reduction of CO₂.