Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents

The acetonitrile-solvated [(MeCN)Ni(C2F5)3]– was prepared in order to compare and contrast its reactivity with the known [(MeCN)Ni(CF3)3]– towards organic electrophiles. Both [(MeCN)Ni(CF3)3]– and [(MeCN)Ni(C2F5)3]– successfully react with aryl iodonium and diazonium salts as well as alkynyl iodonium salts to give fluoroalkylated organic products. Electrochemical analysis of [(MeCN)NiII(C2F5)3]– suggests that, upon electro-oxidation to [(MeCN)nNi(C2F5)3], reductive homolysis of a perfluoroethyl radical occurs, with the concomitant formation of [(MeCN)Ni(C2F5)2]. Catalytic C-H trifluoromethylations of electron rich arenes were successfully achieved using either [(MeCN)Ni(CF3)3]– or the related [Ni(CF3)4]2–. Stoichiometric reactions of the solvated nickel complexes reveal that “ligandless” nickel is exceptionally capable of serving as reservoir of CF3 anions or radicals under catalytically relevant conditions.