Synthesis of two tripodal amine-phosphine ligands for the stabilization of Fe-P and Fe-V bonds

Abstract

Bonds between metals and supporting elements are thought to play an important role in reactivity of catalysts and enzyme active sites. Iron catalysts are of particular interest, iron being cheap, abundant, and environmentally benign.1 While natural iron-based enzymes such as MoFe-nitrogenase are known to facilitate small molecule activation, synthetic analogs are scarce, due in part to the lack of understanding of the role of supporting elements. To elucidate this role, attempts were made to synthesize and characterize molecules containing an iron atom bound to a supporting atom, held together by a tridentate ligand framework containing amine and phosphine binding sites. Of two ligand syntheses that were attempted, one was successful. Attempts were made to insert in this ligand both phosphorus and vanadium as the supporting element to iron. 1H NMR and 1P NMR spectra indicated that while formation of P-Fe and V-Fe complexes may have been successful, neither pure complex was isolated.