VANADIUM(IV) COMPLEXES WITH MIXED O,S DONOR LIGANDS - SYNTHESES, STRUCTURES, AND PROPERTIES OF THE ANIONS TRIS(2-MERCAPTO-4-METHYLPHENOLATO)VANADATE(IV) AND BIS(2-MERCAPTOPHENOLATO) OXOVANADATE(IV)

Reaction of VO(acac)(2) with 2-mercaptophenol (mpH(2)) in the presence of triethylamine gives the mononuclear tris complex (Et(3)NH)(2)[V(mp )(3)] (1), in which the vanadyl oxygen has been displaced. An analogou s reaction using 2-mercapto-4-methylphenol (mmpH(2)) afforded (Et(3)NH )(PNP)[V(mmp)(3)] (2), which was structurally characterized. 2 crystal lizes in the orthorhombic space group Pna2(1) with unit cell parameter s (at -163 degrees C) a = 23.974(7) Angstrom, b = 9.569(4) Angstrom, c = 25.101(6) Angstrom, and Z = 4. The coordination geometry around the vanadium is between octahedral and trigonal prismatic. Reaction of VO (acac)(2) with the sodium salt of 2-mercaptophenol produces the vanady l(IV) complex Na(Ph(4)P)[VO(mp)(2)]. Et(2)O (3), which crystallizes in the triclinic space group <P(1)over bar > with unit cell parameters ( at -135 degrees C) a = 12.185(4) Angstrom, b = 12.658(4) Angstrom, c = 14.244(4) Angstrom, alpha = 103.19(2)degrees, beta = 100.84(2)degrees , and gamma = 114.17(2)degrees. The unit cell of 3 contains a pair of symmetry-related [VO(mp)(2)](2-) units bridged through vanadyl and lig and oxygen atoms by a pair of sodium ions, in addition to two PPh(4)() ions. The coordination geometry around the vanadium is square pyrami dal, with a V=O bond length of 1.611(5) Angstrom. 1, 2, and 3 are char acterized by IR and UV-vis spectroscopies, magnetic susceptibility, EP R spectroscopy, and cyclic voltammetry. 1 and 2 can be oxidized by I-2 , Cp(2)Fe(+), or O-2 to [V(mp)(3)](-) and [V(mmp)(3)](-), respectively , which in turn can be reduced back to the dianions by oxalate ion. Th ese reversible redox processes can be followed by UV-vis spectroscopy.