Bernhardt B, Schauermann M, Solel E, Eckhardt AK, Schreiner PR. Equilibrating parent aminomercaptocarbene and CO
2 with 2-amino-2-thioxoacetic acid
via heavy-atom quantum tunneling.
Chem Sci 2022;
14:130-135. [PMID:
36605744 PMCID:
PMC9769125 DOI:
10.1039/d2sc05388h]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 11/17/2022] [Indexed: 11/19/2022] Open
Abstract
The search for methods to bind CO2 and use it synthetically as a C1-building block under mild conditions is an ongoing endeavor of great urgency. The formation of heterocyclic carbene-carbon dioxide adducts occurs rapidly when the carbene is generated in solution in the presence of CO2. Here we demonstrate the reversible formation of a complex of the hitherto unreported aminomercaptocarbene (H2N-C̈-SH) with CO2 isolated in solid argon by photolysis of 2-amino-2-thioxoacetic acid. Remarkably, the complex disappears in the dark as deduced by time-dependent matrix infrared measurements, and equilibrates back to the covalently bound starting material. This kinetically excluded process below ca. 8 K is made possible through heavy-atom quantum mechanical tunneling, as also evident from density functional theory and ab initio computations at the CCSD(T)/cc-pVTZ level of theory. Our results provide insight into CO2 activation using a carbene and emphasize the role of quantum mechanical tunneling in organic processes, even involving heavy atoms.
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