Molecular Wire Consisting of a C₈ Chain of Elemental Carbon Bridging Two Metal Centers:  Synthesis and Characterization of [{Fe(η⁵-C₅Me₅)(dppe)}₂(μ-C₈)]

The diiron complex [{Fe(η 5 -C 5 Me 5 )(dppe)} 2 (μ-C 8 )] ( 5; dppe = 1,2-bis(diphenylphosphino)ethane) is synthesized by the oxidative coupling of Fe(η 5 -C 5 Me 5 )(dppe)(C⋮CC⋮CH) ( 4 ), and it is established from the properties of the thermally stable mixed-valence complex [Fe II −C 8 -Fe III ][PF 6 ] ( 6 ) that the C 8 chain acts as a molecular wire between the two metal centers, giving rise to the strongest electronic coupling through nine bonds known to date.