(MU-OXO) (MU-CARBOXYLATO) DIIRON(III) COMPLEXES - EFFECTS OF THE TERMINAL LIGANDS

A series of (mu-oxo) (mu-carboxylato) diiron(III) complexes [Fe2(L)2O(OBz)]n+ were synthesized and characterized, where the terminal ligand L represents the ligand N,N-bis(2-pyridylmethyl) glycine (BPG), N,N-bis(2-pyridylmethyl)-3-aminopropionic acid (BPP) and N-carboxymethyl-N-(2-pyridylmethyl) glycine (PDA). The BPG complex was characterized crystallographically: [Fe2O(BPG)2(OBz)](CIO4).3(CH3OH) crystallizes in the monoclinic space group P2(1)/c with a = 12.008 (3) angstrom, b = 21.803 (6) angstrom, c = 16.965 (5) angstrom and beta = 107.09 (2)degrees. The other complexes were characterized by their H-1 NMR, electronic, and Raman spectra. This series, taken together with the analogous tris (2-pyridylmethyl) amine (TPA) complex, provides insight into the effect of the terminal carboxylates on the electronic spectral transitions of the (mu-oxo) (mu-carboxylato)-diiron(III) unit and is useful for understanding the visible spectrum of the diiron site in ribonucleotide reductase.