Formation of a Hexacarbonyl Diiron Complex Having a Naphthalene-1,8-bis(phenylphosphido) Bridge and the Electrochemical Behavior of Its Derivatives

The P–P bond of the cis-1 ligand in (μ-cis-1)[Fe(CO)4]2 (cis-1 = naphthalene-1,8-diphenyldiphosphine) was cleaved by the two iron centers after CO dissociation from the iron centers, although the P–P bond of cis-1 was stereochemically stabilized with a robust naphthalene group, unlike the usual diphosphines, which lack such support. The resulting (μ-nabip)[Fe(CO)3]2 (3; nabip = naphthalene-1,8-bis(phenylphosphido)) had the diiron core linked by the bisphosphido bridge. Since the trans isomer (μ-trans-1)[Fe(CO)4]2 was stable under ambient conditions, the cis disposition of the two Fe(CO)4 fragments was responsible for the cleavage of the P–P bond. The one or two terminal CO ligands of 3 can be replaced by MeCN and a range of phosphine ligands: i.e., PMe3, PPh3, cis-1, and trans-1. Interestingly, it was found that the diphosphine cis-1 could coordinate the iron center in an unusual κ2 fashion to form a three-membered ring, which was confirmed by NMR spectra as well as X-ray analysis. These diiron complexes ...