Electronic Coupling in Dimetallic Complexes with π-Conjugated Bridge

Compound 2, [(η5-C5Me5) Fe(dppe)]2 (μ-C≡C–CH=CH–C≡C), was prepared by the reaction of compound 1, [η5-C5Me5) Fe(dppe)]+2 (μ2-C=CH–CH=CH–HC=C) · (PF 6)2–, with KOBut. Compound 2 showed two quasi-reversible one-electron oxidations at −0.674 and −0.253 V, respectively. The comproportionation constant, Kc, was calculated from these measurements. The mixed-valence(MV) radical cation 2+ showed an absorption peak at 1586 nm, which was assigned to the MV π–π band of the delocalized complex (Robin-Day Mixed-valence Class III) and the effective coupling parameter, Hab, is consistent with the presence of electronic delocalization.