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)

Abstract

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 analogous reaction using 2-mercapto-4-methylphenol (mmpH(2)) afforded (Et(3)NH)(PNP)[V(mmp)(3)] (2), which was structurally characterized. 2 crystallizes in the orthorhombic space group Pna2(1 )with unit cell parameters (at -163 degrees C) a = 23.974(7) Å, b = 9.569(4) Å, c = 25.101(6) Å, 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 vanadyl(IV) complex Na(Ph(4)P)[VO(mp)(2)].Et(2)O (3), which crystallizes in the triclinic space group P&onemacr; with unit cell parameters (at -135 degrees C) a = 12.185(4) Å, b = 12.658(4) Å, c = 14.244(4) Å, 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 ligand oxygen atoms by a pair of sodium ions, in addition to two PPh(4)(+) ions. The coordination geometry around the vanadium is square pyramidal, with a V=O bond length of 1.611(5) Å. 1, 2, and 3 are characterized by IR and UV-vis spectroscopies, magnetic susceptibility, EPR 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. These reversible redox processes can be followed by UV-vis spectroscopy.

A journey into the electrochemistry of vanadium compounds

“…Complexes of vanadium with ligands that provide a mix of O and S donors are rare but interesting, in light of the related and sometimes different features of otherwise identical ligands with O-O and O-S donor atoms. 2-Sulfanylbenzenol (mphH 2 ) and 4-methyl-2-sulfanylbenzenol (mmphH 2 ) gave V(IV) complexes without vanadyl oxygen [102]. The cyclic voltammogram of [V(mmph) 3 ] 2− in MeCN solution vs Ag + /Ag showed a reversible one-electron process and irreversible reduction at −1.08 V (Table 3, entries 6,7), together with oxidations (at +0.59, +0.81, and +1.49 V), that resulted ligand-centered.…”

Synthesis, characterization, magnetic, thermal and redox properties of oxovanadium(IV) complex of heterocyclic acid hydrazone

“…A band at 1590 cm -1 is due to new ν(C=N) (Figure 3). The complex exhibits a broad band at 3070 cm -1 and this is due to the presence of lattice water [15][16][17][18]. In the free ligand 2-thiophenecarbanicotinic hydrazone, thiophene ring shows absorption band at 846 cm -1 .…”

Synthesis and spectroscopic studies of oxovanadium(IV) and dichlorovanadium(IV) complexes of p-X-phenyl-2-picolylketones

“…Such a band position for m(V@O) is usually associated with either the presence of a sixth ligand trans to the vanadyl oxygen, a trigonal bipyramidal geometry, or the presence of a Á Á ÁV@OÁ Á ÁV@OÁ Á Á linear polymer [10,11]. According to the spectral studies and elemental analysis for these complexes and the data reported for similar complexes, we assign this band to the presence of a Á Á ÁV@OÁ Á ÁV@OÁ Á Á polymeric chain [10][11][12][13][14]. The coexistence of monomeric and polymeric forms is consistent with the dissociation of the polymeric brownish red form to the olive green monomeric form as observed from the color change upon grinding.…”