Electrochemical C-H bond activation via cationic iridium hydride pincer complexes

Brian M Lindley; Andrew G Walden; Ann Marie Brasacchio; Andrea Casuras; Nicholas Lease; Chun-Hsing Chen; Alan S Goldman; Alexander J M Miller

doi:10.1039/c9sc03076j

Electrochemical C-H bond activation via cationic iridium hydride pincer complexes

Chem Sci. 2019 Aug 20;10(40):9326-9330. doi: 10.1039/c9sc03076j. eCollection 2019 Oct 28.

Authors

Brian M Lindley¹, Andrew G Walden^{1

2}, Ann Marie Brasacchio^{1

3}, Andrea Casuras⁴, Nicholas Lease⁴, Chun-Hsing Chen¹, Alan S Goldman⁴, Alexander J M Miller¹

Affiliations

¹ Department of Chemistry , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599-3290 , USA . Email: ajmm@email.unc.edu.
² Oglethorpe University , Atlanta , Georgia 30319 , USA.
³ High Point University , High Point , NC 27262 , USA.
⁴ Rutgers, The State University of New Jersey , New Brunswick , New Jersey 08903 , USA.

Abstract

A C-H bond activation strategy based on electrochemical activation of a metal hydride is introduced. Electrochemical oxidation of ( ^tBu₄ PCP)IrH₄ ( ^tBu₄ PCP is [1,3-( ^t Bu₂PCH₂)-C₆H₃]^-) in the presence of pyridine derivatives generates cationic Ir hydride complexes of the type [( ^tBu₄ PCP)IrH(L)]⁺ (where L = pyridine, 2,6-lutidine, or 2-phenylpyridine). Facile deprotonation of [( ^tBu₄ PCP)IrH(2,6-lutidine)]⁺ with the phosphazene base tert-butylimino-tris(pyrrolidino)phosphorane, ^t BuP₁(pyrr), results in selective C-H activation of 1,2-difluorobenzene (1,2-DFB) solvent to generate ( ^tBu₄ PCP)Ir(H)(2,3-C₆F₂H₃). The overall electrochemical C-H activation reaction proceeds at room temperature without need for chemical activation by a sacrificial alkene hydrogen acceptor. This rare example of undirected electrochemical C-H activation holds promise for the development of future catalytic processes.