Untersuchungen an Vanadinsäureestern. IV. Spektroskopische Untersuchungen zur Rotationsisomerie bei Alkyloithovanadaten

Abstract

Die IR‐ und Raman‐Spektren der Verbindungen OVCl2O–i‐C3H7, OVCl(O–i‐C3H7)2 und OV (O–i‐C3H7)3 sowie die IR‐, Raman‐, 1H‐NMR‐ und 13C‐NMR‐Spektren von OV(O–t‐C4H9)3 werden mitgeteilt. Aus den Spektren geht hervor, daß die Verbindungen als Gleichgewichtsgemische von Rotationsisomeren vorliegen. Für das Tri‐t‐butylorthovanadat im festen Zustand werden die zwischen den Rotationsisomeren auftretenden Enthalpiediefferenzen aus der Temperaturabhängigkeit der Ramanintensitäten abgeschätzt.

Effects of Excitation Wavelength on the Raman Spectra of Vanadium(V) Oxo Compounds

“…Due to the very low quantum yield of CCD detectors at wavelengths > 1000 nm, no trace for the CH region recorded with an excitation laser wavelength of 780.2 nm is shown on the left side. In general, measured vibrational band positions agree well with the values reported by Witke et al

4 Raman spectra of VOTIP, recorded with six different laser wavelengths in the range 482.5−780.4 nm. Arrows indicate the position of the vanadyl stretching vibrations where changes are easily observed.

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“…In this case, only one VO stretching vibration should be observed. Since investigations of the aggregation behavior of VOTIP using VOTIP/cyclohexane mixtures showed no signs of association, it was claimed that the compound existed in several rotational isomers …”

Characterization of Silica-Supported Vanadium(V) Complexes Derived from Molecular Precursors and Their Ligand Exchange Reactions

“…A second possibility to explain the presence of two ν(VO) bands is the existence of rotational isomers. The molecular mixed chloroalkoxovanadium(V) complexes have been reported to exhibit this kind of isomerism in their infrared spectra . However, it is curious that only one overtone 2ν(VO) is observed in the spectra of our surface species.…”

Syntheses, X-ray Structures, and Solution Properties of [V4O4{(OCH2)3CCH3}3(OC2H5)3] and [V4O4{(OCH2)3CCH3}2(OCH3)6]: Examples of New Ligand Coordination Modes

“…Alkoxide Exchange Studies. Simple oxovanadium alkoxides in general show a high level of lability. ,,, The lability can be decreased by using sufficiently large bulky groups around the vanadium atom 7 however, compounds 1 − 3 are likely to show some differences in their lability since they contain different alkoxy groups. All three tetramers would form VO(OR) 3 when dissolved in alcohol.…”