Novel vanadium(V) homocitrate complex: Synthesis, structure, and biological relevance of [K-2(H2O)(5)][(VO2)(2)(R,S-homocitrate)(2)]center dot H2O

Initial investigations into the possible roles of homocitric acid in the biosynthesis and function of the active site cofactor of nitrogenase resulted in the isolation and characterization of the dinuclear vanadium(V) species [K-2(H2O)(5)][(VO2)(2)(R,S-C7H8O7)2] . H2O ( 1). Complex 1 represents the first synthetic structurally characterized transition metal homocitrate complex and may represent an early mobilized precursor in the biosynthesis of VFeco. Compound 1 was characterized by a variety of physical methods, including X-ray crystallography. Crystal data: space group P (1) over bar (#2), with a = 10.292 (3) Angstrom, b = 16.663 (3) Angstrom, c = 8.343 (1) Angstrom, alpha = 95.93 (1)degrees, beta = 105.74 (2)degrees, gamma = 90.86 (2)degrees, V = 1386 (1) Angstrom(3), and Z = 2. The homocitrate ligand is coordinated to the vanadium(V) atoms in a bidentate fashion via the deprotonated bridging hydroxyl group and a carboxylate donor. This unique coordination mode accurately mimics the coordination of homocitrate to the cofactor of nitrogenase.