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

Abstract

A new series of oxovanadium(IV) complexes formulated as [(HL) 2 VO] n AE nSO 4 (a), [(HL)VO(SO 4 )] 2 (b), and [L 2 VO] (c), where HL ¼ phenyl-2-picolylketone and its para-substituted derivatives have been synthesized and characterized. The i.r. data suggest that the ligands are neutral bidentate in classes (a) and (b) and uninegative bidentate in (c), coordinated to the vanadyl ion via the pyridine-N and keto-or enolato-O atoms. Complexes of class (a) showed mechanochromism upon grinding. Magnetic, u.v./vis. and e.s.r. data suggest that all the complexes have a square pyramidal structure with an unpaired electron in the d xy orbital in the solid and in solutions. Deoxygenation of the oxovanadium complexes gave the corresponding dichlorovanadium(IV) derivatives. Elemental analysis, magnetic and spectral studies indicated that the dichlorovanadium(IV) complexes are associated with a distorted transoctahedral ligand field.

Thermochemical Considerations of Metal Enolates

“…An example of fortuitous vanadium enolate chemistry is the CO addition reaction to a silylamido vanadium species in which the dimeric metallocycle 32 is transformed 192 More conventional species 195 are the spectroscopically, magnetically and structurally characterized vanadyl bis(picolinylketone) enolate complexes 34, and the related complexes formed by their protonation. These species have also been converted into their VCl 2 derivatives 35.…”

Synthesis and characterization of two new types of oxovanadium complexes with pyrazole as ligand

“…Signals at 1540 cm −1 (assigned to ν C=N and ν C=C ) and 798 cm −1 (attributed to δ C-H ) correspond to monodentate pyrazole units, and as the pyrazoles are not deprotonated, the ν N-H band is observed at 3145 cm −1 [18] . The ν O-S in the group of SO 4 2− was indicated at 1126 cm −1 [27] . The bands at 458 and 350 cm -1 were assigned to ν V-N and ν V-O respectively.…”

“…The spectra exhibit SO 4 2− bands at 1197 and 1098 cm −1 suggesting bidentate coordination of SO 4 2-. The bands at 420-480 and 284-380 cm −1 are assigned to ν V-N and ν V -O , respectively [27] . The broad band at 3289 cm −1 is attributed to strong hydrogen-bond there.…”

Vibrational spectra of transition element compounds

“…156 VO(L)(HL) has nVQO at 957 cm À1 , where H 2 L = (4). [167][168][169][170][171][172][173][174][175][176] Skeletal mode assignments have been proposed for [(VO 2 )(dipic)] 2 2À , where H 2 dipic = (8), from IR and Raman spectra, including n s VO 2 862, 849 cm À1 , n as VO 2 965 cm À1 , nVO (carboxylate) 456 cm À1 , nV-N 367 cm À1 . 158 The IR spectrum of [(VO) 12 42 ] 6À has nVQO at 945 cm À1 , n s V-O-V 785 cm À1 , and n as V-O-V 687 cm À1 .…”