Acceleration Effect of Bases on Mn Pincer Complex-Catalyzed CO2 Hydroboration

Zixing Jia; Longfei Li; Xuewen Zhang; Kan Yang; Huidong Li; Yaoming Xie; Henry F Schaefer 3rd

doi:10.1021/acs.inorgchem.1c03614

Acceleration Effect of Bases on Mn Pincer Complex-Catalyzed CO₂ Hydroboration

Inorg Chem. 2022 Mar 7;61(9):3970-3980. doi: 10.1021/acs.inorgchem.1c03614. Epub 2022 Feb 25.

Authors

Zixing Jia¹, Longfei Li¹, Xuewen Zhang¹, Kan Yang¹, Huidong Li², Yaoming Xie³, Henry F Schaefer 3rd³

Affiliations

¹ College of Pharmacy, Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Hebei University, Baoding 071002, Hebei, P. R. China.
² Research Center for Advanced Computation, School of Science, Xihua University, Chengdu 610039, P. R. China.
³ Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602, United States.

PMID: 35212516
DOI: 10.1021/acs.inorgchem.1c03614

Abstract

Herein, we report a comprehensive study of CO₂ hydroboration catalyzed by Mn pincer complexes. The traditional metal-ligand cooperation (MLC) mechanism based on the H-Mn-N-Bpin pincer complex is not viable due to the competing abstraction of the Bpin group from the H-Mn-N-Bpin complex by NaO^tBu. Instead, we propose an ionic mechanism based on the H-Mn-N-Na species with a low energy span (22.5 kcal/mol) and unveil the acceleration effect of bases. The X groups in the H-Mn-N-X catalyst models are further modulated, and the steric hindrance and H→B donor-acceptor interactions of the X group increase the energy barrier of the hydride transfer. The hydrogen bond and electrostatic interactions of the X group can accelerate the hydride transfer to HCOOBpin and HCHO molecules except for the nonpolar CO₂ molecule. Based on these discoveries, we designed a pyridine-based Mn pincer catalyst system, which could achieve CO₂ hydroboration in low-temperature and base-free conditions through a metal-ligand cooperation mechanism.