Reactivity of a Series of Isostructural Cobalt Pincer Complexes with CO_2, CO, and H^+
David W. Shaffer, Samantha I. Johnson, Arnold L. Rheingold, Joseph W. Ziller, William A. Goddard III, Robert J. Nielsen, Jenny Y. Yang
Abstract
The preparation and characterization of a series of isostructural cobalt complexes Co(t-Bu)_2(P^EPy^EP)(t-Bu)_2(CH_3CN)_2]-[BF_4]_2 (Py = pyridine, E = CH_2, NH, O, and X = BF_4 (1a-c)) and the corresponding one-electron reduced analogues Co(t-Bu)_2P^EPy^EP(t-Bu)_2(CH_3CN)_2][BF_4]_2 (2a-c) are reported. The reactivity of the reduced cobalt complexes with CO_2, CO, and H^+ to generate intermediates in a CO_2 to CO and H_2O reduction cycle are described. The reduction of 1a-c and subsequent reactivity with CO_2 was investigated by cyclic voltammetry, and for 1a also by infrared spectroelectrochemistry. The corresponding CO complexes of (2a-c) were prepared, and the Co-CO bond strengths were characterized by IR spectroscopy. Quantum mechanical methods (B3LYP-d3 with solvation) were used to characterize the competitive reactivity of the reduced cobalt centers with H^+ versus CO_2. By investigating a series of isostructural complexes, correlations in reactivity with ligand electron withdrawing effects are made.
Group Members
Shaffer, D. W., Johnson, S. I., Rheingold, A. L., Ziller, J. W., III, W. A. G., Nielsen, R. J., & Yang, J. Y. (2014). Reactivity of a Series of Isostructural Cobalt Pincer Complexes with CO_2, CO, and H^+. *Inorg. Chem.*, *53*(24), 13031-13041.