SYNTHESIS AND CHARACTERIZATION OF VANADIUM(II,III,IV) COMPLEXES OF PYRIDINE-2-THIOLATE

The synthesis and characterization are reported of vanadium complexes of pyridine-2-thiolate (pyt(-)) with the metal in oxidation states II, III, and IV. The reaction of VOCl2(THF)(2) with 2 equiv of Na(pyt) in THF leads to formation of [V2O2(pyt)(4)] (1). Complex 1 . 2THF . 1/3C(6)H(12) crystallizes in hexagonal space group R (3) over bar with the following cell dimensions at -171 degrees C: a = b = 30.888(21) Angstrom, c = 8.960(6) Angstrom, Z = 9, and V = 7402.8 Angstrom(3). A total of 1310 unique reflections with F > 2.33 sigma(F) were employed for structure solution and refinement to R (R(W)) values of 0.0613 (0.0563). The structure consists of two VO(pyt)(2) units joined together by two monoatomic bridges provided by S atoms of two pyt(-) groups. The V .. V distance is 3.989(2) Angstrom. The reaction of VCl3(THF)(3) with four equivalents of Na(pyt) in THF gives [VNa(pyt)(4)(THF)(2)] (2). Complex 2 crystallizes in triclinic space group P (1) over bar with the following unit cell dimensions at -171 degrees C: a = 10.442(2) Angstrom, b = 16.476(4) Angstrom, c = 9.465(2)Angstrom, alpha = 100.73(4)degrees, beta = 109.20(4)degrees, gamma = 87.86(3)degrees, Z = 2, and V = 1510.3 Angstrom(3). A total of 3391 unique reflections with F > 2.33 sigma(F) were employed for structure solution and refinement to R (R(W)) values of 0.0412 (0.0431). The structure is best described as a heterodinuclear complex with the metals monoatomically bridged by S atoms from three pyt(-) groups. The V is seven-coordinate, and the Na is six-coordinate. The V .. Na distance is 3.516(1) Angstrom. The reaction of VCl2(tmeda)(2) (tmeda = tetramethylethylenediamine) with 2 equiv of Na(pyt) in THF or CH2Cl2 yields [V(pyt)(2)(tmeda)] (3). Complex 3 crystallizes in orthorhombic space group B22(1)2 with the following cell dimensions at -170 degrees C: a = 14.338(5) Angstrom, b = 17.755(7) Angstrom, c = 7.255(2) Angstrom, Z = 4, and V = 1846.9 Angstrom(3). A total of 1192 unique reflections with F > 2.33 sigma(F) were employed for structure solution and refinement to R (R(W)) values of 0.0220 (0.0261). The complex contains chelating pyt(-) and tmeda groups with severely distorted octahedral geometry. Complexes 1, 2, and 3 have been characterized by EPR and/or IR spectroscopy. In addition, mass spectral studies are described for 1 and 2, directed toward identifying fragmentation pathways involving C-S bond cleavage within the pyt(-) group; the latter cleavage is detected in the mass spectra of both compounds.