Exploring the feasibility of N_2 fixation at single and multiple iron sites

Abstract

Of central interest to hypotheses concerning iron's role in biol. nitrogen fixation are the accessible geometries and oxidn. states of proposed iron intermediates. Indeed, a key longstanding goal of coordination chem. is to map the types of metal complexes that can be anticipated to have reasonable stability and to elucidate their reactivity patterns. Such information drives to the heart of mechanistic postulates for transformations that occur in metalloenzymes as complex as nitrogenase. Our group has an ongoing interest in exploring and hopefully expanding the boundaries of the types Fe-N_xH_y species that can be generated and characterized. These types of species find broader context with respect to proposed pathways for biol. nitrogen fixation. My lecture will specifically focus on results from our lab pertaining to the types of Fe-N_xH_y complexes that are accessible for 4- and 5-coordinate geometries. In particular, I will discuss what we now know about some rather unusual formal oxidn. states and spin states that are synthetically available for low-coordinate iron featuring N_2 or N_2-related ligands, ranging from Fe(I) to Fe(IV), and whether such species motivate new hypotheses for the mode nitrogen fixation at the cofactor.

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