N−N Bond Cleavage in Diazoalkanes by a Bis(imino)pyridine Iron Complex

Abstract

Addition of monosubstituted diazoalkanes, N(2)CHR (R = Ph, p-Tolyl, (t)Bu, Cy), to the bis(imino)pyridine iron dinitrogen complex, ((iPr)PDI)Fe(N(2))(2), at 23 degrees C in benzene-d(6) resulted in rapid cleavage of the N-N bond to yield the iron nitrile and imine complexes, ((iPr)PDI)FeNCR and ((iPr)PDI)FeHNCHR, respectively. Aryl azines were also cleaved with ((iPr)PDI)Fe(N(2))(2) and yielded the same products. Mechanistic studies support a pathway involving initial formation of an iron alkylidene followed by rapid [4pi + 2pi] cycloaddition with another equivalent of diazoalkane. Subsequent rate-determining 1,3-hydrogen migration followed by retrocycloaddition yields the observed products.