Simultaneous two-hydrogen transfer as a mechanism for efficient CO(2) reduction.
Two-hydrogen transfer (simultaneous protic and hydridic hydrogen transfer) is examined as a potentially efficient mechanism for the selective reduction of CO(2) to methanol. High-level ab initio CCSD(T) coupled-cluster theory simulations of ammonia-borane (AB), which contains both protic and hydridic hydrogen, show the effectiveness of this mechanism. AB demonstrates how simultaneous two-hydrogen transfer is kinetically efficient because (1) two-hydrogen transfer avoids high-energy single-electron-reduced intermediates, (2) the CO(2)'s HOMO is protonated while the LUMO is concurrently reduced by a hydride, and (3) complementary charge polarities around the six-membered-ring transition-state structures stabilize the transition states. This study suggests that an effective mechanism for the reduction of CO(2) to methanol proceeds through three two-hydrogen-transfer steps and that suitable catalysts should be developed that exploit two-hydrogen transfer without the use of AB.
Zimmerman
Paul M
PM
Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.
Zhang
Zhiyong
Z
Musgrave
Charles B
CB
D000641:Ammonia / Q000737:chemistry; D001880:Boranes / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D000432:Methanol / Q000138:chemical synthesis* / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D010084:Oxidation-Reduction; D011789:Quantum Theory
D001880:Boranes; D002245:Carbon Dioxide; D000641:Ammonia; D006859:Hydrogen; D000432:Methanol