A phosphine-free molecularly-defined Ni(II) complex in catalytic hydrogenation of CO 2 .

The development of base metal catalysts capable of CO 2 hydrogenation is a challenge and a necessity to progress from the scarce noble metal catalysts. In this regard, we report herein the first non-phosphine-based Ni complex, supported by a "carbazolato-bis-NHC" pincer ligand framework, for efficient catalytic hydrogenation of CO 2 to formate. A tailored combination of the Ni complex as a catalyst, DBU as a base, and Zn(OAc) 2 as an additive offered enhanced activity leading to a TON up to 5476 and an excellent yield up to 92% for the formate product from a reaction on ∼27 mmol scale.