| Stoichiometric reactions between alkyl halides (primary and secondary alkyl monohalides, alpha,o-dihaloalkanes, and alpha,alpha '-dibromoxylenes) and electrogenerated [[2,2'-[1,2-ethanediylbis(nitrilomethylidyne)]bis[phenolato]]- N,N',O,O']nickelate(I), or nickel(I) salen, in aprotic solvents containing tetraalkylammonium salts have been probed. A variety of electrochemical and other analytical techniques was employed for this study, including cyclic voltammetry, controlled-potential electrolysis, in situ ultraviolet-visible spectrophotometry, and high-performance liquid chromatography. With the aid of mass spectrometry, gas chromatographic analysis reveals that exposure of an electrolyzed solution of nickel(I) salen and an alkyl monohalide (primary and secondary) to oxygen results in the formations of an aldehyde and a ketone, respectively, whereas a cycloalkane arises mainly from the alpha,o-dihaloalkane-nickel(I) salen system. Alkanes and alkenes are other compounds formed via these reactions. Effects of the substrate-nickel(I) salen ratio, light, temperature, water, and proton donors as well as experiments involving isotopically labeled reagents have been explored to improve the yield of a desired aldehyde and to elucidate mechanistic details of these reactions. For comparison, cobalt(I) salen and other square-planar nickel(I) complexes were utilized to reduce these alkyl halides. |
