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Isolation and X-ray Crystal Structure of an Electrogenerated TEMPO–N3 Charge-Transfer Complex

preprint
revised on 13.04.2020 and posted on 16.04.2020 by Hosea Nelson, Juno Siu, Ambarniel Saha, Duilio Cascio, Song-Bai Wu, Chenxi Lu, Jose A. Rodriguez, Kendall N Houk, Song Lin
Recent advances in radical-based catalytic reactions have created an increasing demand for the understanding of their mechanistic underpinnings. Structural elucidation of transient reactive intermediates via diffraction techniques, though rarely possible, is one of the most decisive ways to support such mechanistic hypotheses. Here we present the isolation, structural elucidation, and theoretical analysis of an electrochemically generated and catalytically relevant charge-transfer species formed between the azidyl radical and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO). The unusual bent N–N–N angle and the pancake bonding between these two fragments highlight the weak bonding interactions present in this complex. This X-ray structure validates computational predictions as well as mechanistic proposals of TEMPO-mediated radical azidation reactions.

Funding

CHE-1751839

CHE-1764328

DGE-1650604

Bristol-Myers Squibb

History

Email Address of Submitting Author

jcs529@cornell.edu

Institution

Cornell University

Country

United States

ORCID For Submitting Author

0000-0003-4675-5399

Declaration of Conflict of Interest

None

Version Notes

Revised SI

Exports