Effective Pincer Cobalt Precatalysts for Lewis Acid Assisted CO2 Hydrogenation

Effective Pincer Cobalt Precatalysts for Lewis Acid Assisted CO2 Hydrogenation

Ariana Z. Spentzos, Charles L. Barnes, and Wesley H. Bernskoetter*

University of Missouri

http://pubs.acs.org/doi/pdf/10.1021/acs.inorgchem.6b01454

Inorg. Chem. 

DOI: 10.1021/acs.inorgchem.6b01454

TOC:


Abstract:

The pincer ligand MeN[CH2CH2(PiPr2)]2 (iPrPNP) was employed to support a series of cobalt(I) complexes, which were crystallographically characterized. A cobalt monochloride species, (iPrPNP)CoCl, served as a precursor for the preparation of several cobalt precatalysts for CO2 hydrogenation, including a cationic dicarbonyl cobalt complex, [(iPrPNP)Co(CO)2]+. When paired with the Lewis acid lithium triflate, [(iPrPNP)Co(CO)2]+ affords turnover numbers near 30 000 (at 1000 psi, 45 °C) for CO2-to-formate hydrogenation, which is a notable increase in activity from previously reported homogeneous cobalt catalysts. Though mechanistic information regarding the function of the precatalysts remains limited, multiple experiments suggest the active species is a molecular, homogeneous [(iPrPNP)Co] complex.

Research Progress on the Indirect Hydrogenation of Carbon Dioxide to Methanol

Xian-Long Du, Zheng Jiang, Dang Shen Su, Jian-Qiang Wang

First published: 21 December 2015   DOI: 10.1002/cssc.201501013

Abstract

Methanol is a sustainable source of liquid fuels and one of the most useful organic chemicals. To date, most of the work in this area has focused on the direct hydrogenation of CO₂ to methanol. However, this process requires high operating temperatures (200–250 °C), which limits the theoretical yield of methanol. Thus, it is desirable to find a new strategy for the efficient conversion of CO₂ to methanol at relatively low reaction temperatures. This Minireview seeks to outline the recent advances on the indirect hydrogenation of CO₂ to methanol. Much emphasis is placed on discussing specific systems, including hydrogenation of CO₂ derivatives (organic carbonates, carbamates, formates, cyclic carbonates, etc.) and cascade reactions, with the aim of critically highlighting both the achievements and remaining challenges associated with this field.

http://onlinelibrary.wiley.com/doi/10.1002/cssc.201501013/full

Synthesis and Characterization of Pincer-Molybdenum Precatalysts for CO2 Hydrogenation

Synthesis and Characterization of Pincer-Molybdenum Precatalysts for CO2 Hydrogenation

Yuanyuan Zhang†‡, Paul G. Williard‡, and Wesley H. Bernskoetter*†‡
† Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States
‡ Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
Organometallics, Article ASAP
DOI: 10.1021/acs.organomet.5b00955
Publication Date (Web): January 19, 2016








A family of low-valent molybdenum complexes supported by the pincer ligand PNMeP (PNMeP = MeN(CH2CH2PPh2)2) was prepared and characterized, including (PNMeP)Mo(C2H4)2, which contains an agostic interaction between the metal and the N-methyl substituent. This β-agostic C–H bond was cleaved by molybdenum and produced a cyclometalated molybdenum formate complex, (κ4-PNMeP)Mo(C2H4)(κ2-O2CH), upon exposure to CO2. This species serves as a promotor of CO2 hydrogenation to formate under basic conditions, a rare transformation for group VI metals. The performance of the precatalyst was enhanced with the addition of Lewis acid salts.