Addition of monosubstituted diazoalkanes, N2CHR (R = Ph, p-Tolyl, Bu-tau, Cy), to the bis(imino)pyridine iron dinitrogen complex, ((PDI)-P-iPr)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 nitrite and imine complexes, ((PDI)-P-iPr)FeNCR and ((PDI)-P-iPr)FeHNCHR, respectively. Aryl azines were also cleaved with ((PDI)-P-iPr)Fe(N-2)(2) and yielded the same products. Mechanistic studies support a pathway involving initial formation of an iron alkylidene followed by rapid [4 Pi + 2 Pi] cycloaddition with another equivalent of diazoalkane. Subsequent rate-determining 1,3-hydrogen migration followed by retrocycloaddition yields the observed products.