Entry into the dinitrogen chemistry of sulfur-ligated iron complexes

Although many examples of dinitrogen complexes of transition metals have been reported to date, few contain sulfur-based ligands, and those of iron are particularly uncommon. Such complexes are relevant towards constructing functional and structural models of the FeMo cofactor in nitrogenase, which catalytically reduces dinitrogen to ammonia through a cycle in which dinitrogen binding at iron has been implicated. This presentation describes the synthesis of dinitrogen complexes of iron chelated by the tripodal tetradentate ligands, [SiP^R_Xs^(R')_y-]- ([SiP^R_xS^(R')_y- = (R_2PC_6H_4)_x(R'SC_6H_4)_ySi- : R = iPr, Ph; R' = Ad), which contain one or two thioether arms complemented by phosphine arms. The characterization of several Fe(II) and Fe(I) complexes is presented, and a comparison with the iron dinitrogen chem. of the parent tris(phosphino)silyl ligands, [SiP^R_3]- (SiP^R_3 = (R_2PC_6H_4)_3Si-; R = iPr, Ph) is discussed.