NOVEL VANADIUM(V) HOMOCITRATE COMPLEX - SYNTHESIS, STRUCTURE, AND BIOLOGICAL RELEVANCE OF O)(5)][(VO2)(2)(R,S-HOMOCITRATE)(2)]CENTER-DOT-H2O

Initial investigations into the possible roles of homocitric acid in t he biosynthesis and function of the active site cofactor of nitrogenas e resulted in the isolation and characterization of the dinuclear vana dium(V) species [K-2(H2O)(5)][(VO2)(2)(R,S-C7H8O7)2] . H2O ( 1). Compl ex 1 represents the first synthetic structurally characterized transit ion metal homocitrate complex and may represent an early mobilized pre cursor 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)degr ees, 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 v anadium(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 n itrogenase.