Binuclear electron reservoir complexes. Synthesis, stabilization and electronic structures of the 36- and 37-electron complexes [[Fe(C5R5)]2(.mu.2,.eta.n-C10H8)]m+ (R = H, Me): from biphenyl (m = 1 and 2, n = 12) to bicyclohexadienylidene (m = 0, n = 10)

The reduction of [(FeCp) 2 (biphenyl)] 2+ (2a 2+ ) was found to be a chemically and elecrochemically reversible two-electron process by cyclic voltammetry in DMF at −38 o C. The 2e reduction of the new complex [(FeCp * ) 2 (biphenyl)] 2+ (PF 6 − ) 2 (2b 2+ ), using Na/Hg in THF at 20 o C gives the ESR-silent stable blue diamagnetic complex 2b, analogous to 2a, whereas the cyclic voltammogram of 2b 2+ shows close reversible one-electron waves. The complex 2b was shown by 1 H and 13 C NMR and Mossbauer spectroscopy to have a 36e Fe 2 II bicyclohexadienylidene structure