Nickel()-mediated oxidative cascades from a thiol-bearing nickel() precursor to the nickel() product

• Published in: Dalton transactions : an international journal of inorganic chemistry 2018, Vol.47 (11), p.3796-382
• Main Authors: Chang, Hao-Ching, Lin, Sheng-Hsiang, Hsu, Yu-Chen, Jen, Shao-Wei, Lee, Way-Zen
• Format: Article
• Language: English
• Subjects: Absorption spectra; Cascades; Diamagnetism; Electron transfer; Nickel; Oxidation; Precursors; Thiols; Valence
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c7dt04137c

A nickel( ii ) complex, Ni(HPS2) 2 ( 1 ) that contains two pendant thiols, is rapidly aerobically oxidized in the presence of an amine to produce a diamagnetic nickel( iv ) complex, Ni(PS2) 2 ( 2 ). This process was investigated spectroscopically at a temperature of −80 °C. Absorption spectra revealed that the deprotonation of one pendant thiol of 1 triggers an oxidative cascade; EPR findings indicate that single-spin species comprised of nickel( iii ) intermediates are produced in the reaction solution. Possible reaction routes were examined by DFT calculations, in which an energy profile indicates that (i) a self-driven formation of 2 favors a sequential proton/electron transfer pathway; (ii) kinetically trapped nickel( iii ) intermediates may respond to the specificity of the coordination of 2 in a cis -form. The overall findings help one to rationalize how a nickel( ii ) precursor can be oxidized by O 2 to a higher oxidation state. Triggered by deprotonation, a nickel( ii ) complex, Ni(HPS2) 2 ( 1 ) that contains two pendant thiols, is rapidly aerobically oxidized to a diamagnetic nickel( iv ) complex, Ni(PS2) 2 ( 2 ), through EPR-active nickel( iii ) intermediates.