A Cobalt(II) Complex Bearing the Amine(imine)diphosphine PN(H)NP Ligand for Asymmetric Transfer Hydrogenation of Ketones
Shangfei Huo, Hong Chen, Weiwei Zuo
Abstract
Novel chiral cobalt complex a containing amine(imine)diphosphine PN(H)NP ligand and complex b containing bis(amine)diphosphine PN(H)N(H)P ligand were synthesized. The structures of two complexes were characterized by X‐ray crystallography and high resolution mass spectrometry. The catalytic performances of cobalt complexes a and b for asymmetric transfer hydrogenation (ATH) of ketones under mild conditions were evaluated using 2‐propanolisopropanol as solvent and hydrogen source after being activated by 8 equivalents of base. Complex a showed a good reactivity for reduction of ketones, with a turnover number (TON) of up to 555, and a maximum enantiomeric excess ( ee ) value of up to 91 %. Complex b exhibited inertness for hydrogenation of ketones. Electronic structure studies on a and b were conducted to account for the function of ligands on the catalytic performances.