Heptacoordinate vanadium(III) complexes containing a didentate sulfate ligand. X-ray structures of [V-2(SO4)(3){N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine}(2)] and [V(SO4){N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine}](+) and their solution properties

Several vanadium(III) complexes with a tetradentate N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen) or a hexadentate N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine (tpen) ligand were prepared and characterized by UV-vis and Raman spectroscopy. Of these complexes, the structures of two vanadium(III) complexes with a didentate sulfate were determined by X-ray crystallography. [V-2(SO4)(3)(bispicen)(2)] crystallizes in the monoclinic space group C2/c with a = 25.083(7), b = 24.236(5), c = 15.708(5) Angstrom, beta = 114.96(2)degrees, Z = 8, and R = 0.087. The complex containing the [V(SO4)(tpen)](+) cation crystallizes in the orthorhombic space group Aba2 with a = 20.1836(8), b = 19.793(1), c = 15.6107(7) Angstrom, Z = 8, and R = 0.069. Both complexes adopt a heptacoordinate pentagonal bipyramidal structure in which the didentate sulfate is situated in the pentagonal plane. The heptacoordinate structure of the tpen-SO42- complex is stable in an aqueous solution, whereas the bispicen-SO42- complex is easily aquated to yield a hexacoordinate ore-bridged dinuclear species.