Dinitrogen chemistry from trigonally coordinated iron and cobalt platforms

The chemistry of low-valent iron and cobalt has been slow to develop, due largely in part to a lack of ligand scaffolds that can stabilize these species. Using the anionic tris(phosphino)borate ligand, [PhB(CH_2PiPr_2)_3]-, we have stabilized reactive complexes of the type [P_3M-L] where L can be varied from weakly-donating π-acidic ligands (e.g. N_2), to strongly π-basic ligands where multiple bonding occurs between the metal and L (e.g. NR ^2-). In addition to stabilizing a broad range of ligand types in a variety of oxidation states, the [P_3M] template has been shown to mediate the coordination and activation of dinitrogen on both iron and cobalt. The reaction chemistry of the [P_3M-L] scaffolds will be presented in addition to synthetic strategies targeting high-valent species (M^(IV), L=N ^3-).