Oxidative Cleavage of CH3 and CF3 Radicals from BOXAM Nickel Complexes

• Published in: Organometallics Vol. 31; no. 15; pp. 5334 - 5341
• Main Authors: Klein, Axel, Vicic, David A, Biewer, Christian, Kieltsch, Iris, Stirnat, Kathrin, Hamacher, Claudia
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.08.2012
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om300342r

Oxidation of the nickel complexes [(BOXAM)Ni(R)] (HBOXAM = bis((4-isopropyl-4,5-dihydrooxazol-2-yl)phenyl)amine) with R = CF3, CH3, Cl leads to the corresponding radical cationic complexes, which rapidly undergo homolytic Ni–R bond splitting. The corresponding radicals R• can be generated by either anodic (electrochemical) or aerial oxidation and were detected by spin trapping experiments using N-tert-butyl-α-phenylnitrone (PBN). The splitting reaction was also monitored by UV–vis–near-IR absorption spectroelectrochemistry, showing the formation of the “byproduct” complex [(BOXAM)Ni(THF)]+ in THF solution. Additionally, the undissociated complex radicals [(BOXAM)Ni(R)]•+ were studied by EPR and UV–vis–near-IR spectroelectrochemistry, revealing inter alia largely ligand-centered oxidation. DFT calculations on ground and oxidized states support this finding.