New polypyridine ligands functionalized with redox-active Fe(II) organometallic fragments.

We report in this Communication the isolation and characterization, including structure determinations, of 2,2',6',2"-terpyridine (2) and 2,2'-bipyridine (3) ligands bearing two redox-active "(eta2-dppe)(eta5-C5Me5)FeC[triple bond]C-" moieties grafted to the 5 and 5" positions of terpy or to the 5 and 5' positions of bipy. These "metalloligands" have been complexed with Ru(II) and Mo(0), providing new heterotrinuclear complexes displaying intense absorptions around 700 and 600 nm, respectively, for the Fe2Ru/terpy and Fe2Mo/bipy species. In both cases, the Fe(II)/Fe(III) oxidation potentials of the free ligands became more positive by more than 50 mV upon complexation.