Atomic displacement parameter plots for the single-crystal structures of Cu-1 to Cu-4 shown at 50% probability. The crystal structures were obtained at 100 K, except for Cu-2 (15 K). © 2024 American Chemical Society
Oxygenation of hydrocarbons is the process by which oxygen atoms are added to a hydrocarbon molecule in order to insert oxygen into the structure of the hydrocarbon. This is commonly achieved via a reaction with molecular oxygen (O2), ordinarily using a catalyst to facilitate the process. A variety of mechanisms are employed depending on the desired products and reaction conditions. These include partial oxidation to complete combustion, producing useful compounds like alcohols, aldehydes, ketones, or carboxylic acids. Monometallic copper−oxygen species are well known as hydroxylating agents in biology, but a limited number of synthetic model compounds are known to react with hydrocarbons, owing to high C−H bond dissociation energies.
A team of researchers overcame this obstacle by investigating the photoredox chemistry of monometallic copper (pyrazolyl)borate complexes coordinated by chlorate in the presence of C1−C6 alkanes. Using copper(III) ion, or copper in a +3 oxidation state with hexane as an exemplar, the team showed that photoredox chemistry may be achieved under solar conditions of one-sun illumination.
X-ray diffraction analyses of Cu-1, Cu-2, and Cu-3 were carried out at the Advanced Crystallography x-ray beamline of NSF’s ChemMatCARS at Sector15 of the Argonne Advanced Photon Source. Data for Cu-3 were also collected at the Harvard Department of Chemistry and Chemical Biology X-ray Laboratory using a Bruker APEX DUO diffractometer.
These results confirm the utility of photochemistry in achieving the oxidation of alkanes under mild conditions. By tuning the oxidizing power of the copper-oxyl with the ancillary ligand field, the level of substrate oxidation may be controlled.
See: Daniel L. Nascimento, David Gygi, Matthew C. Drummer, Miguel I. Gonzalez, Shao-Liang Zheng, and Daniel G. Nocera*, “Photoredox Oxidation of Alkanes by Monometallic Copper−Oxygen Complexes Using Visible Light Including One Sun Illumination,” J. Am. Chem. Soc. 146, 28612-28617 (2024).
Author affiliation: Department of Chemistry and Chemical Biology, Harvard University
Correspondence: *dnocera@fas.harvard.edu
This research was supported by the National Science Foundation (NSF) Division of Chemistry (CHE) under the grant number CHE-2243724. We thank the support to the Xray core facility from the Major Research Instrumentation (MRI) Program of the NSF under grant number CHE-2216066. NSF’s ChemMatCARS is supported by the NSF Divisions of Chemistry and Materials Research, under grant number CHE-1834750.
For information on Advanced Crystallography program at NSF’s ChemMatCARS contact:
Yu-Sheng Chen
(630) 252-0471
yushengchen@uchicago.edu