An EPR Study ol Vanadyl Complexes for Advanced Undergraduate Laboratory
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In our advanced lahoratorv course. we teach the nrincioles of the various research instruments. An article in THIS J O U R N A Ipresented .~ the use of two iyrtems fin an EPR erperrment. W e have used a similar experiment, however, with a slighrly dilferent emphbair. We have used the two complexes uf vanadium; vanadium (IV) oryarrtylnretonare. VO(nrar1r. and bisl0.W-diethyldithiophosphato~oxovanadium (IV).'l'hese two compounds farilirate the swdy of rhr same unpaired dl electron liystem while varying the chemical environment. For this experiment. VO(auacl2 was purchased from Alfa Ventron Corporation and bis(0.W-dierhyldithiophosphnmloxovanadium (IV) was prepared arcordinz U)the urwedurev of Wayon2 This vreparatiun is not exceedinrlv rime-ronsumin~ and can introduce the students to a syntKesis of air and water sensitive comp&nd. Necessary precauGons must be taken in the preparation of this unstable species. We prepare the compound under nitrogen atmosphere in previously dried solvents and run the EPR spectrum in the same three-hour laboratory period. All EPR spectra are run on a Varian E-4 spectrometer inn aoh~tioncell. An ei~ht-lineEPR spectrum is ohserved at R.T. for V O t a c a ~ )as ~ ,experted.3 The second compound studied has the following strurture: ~~~
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In this complex the metal ion, the number of coordination sites, and the hasie geometry are kept the same compared with VO(aeac)~,and only the type of atoms attached t o the metal have been changed. Sulfur does not have a nuclear spin and therefore will not cause any hyperfme interactions. However, phwphorus with a nuclear spin of ?hwill cause further splitting. The eight hypefine linesdue to the vanadium splitting are further split by the twoequivalent phwphorus nuclei. This splitting is of interest since even though the phosphorus atoms are not immediately adjacent t o the vanadium atom with its one unpaired electron, interactions are observed. A total of 24 lines should be observed; however, due to overlapping lines, only 17 lines are observed. A g value of 1.963 is calculated. Other references to this eompound can be found in the literatum4"
' Serlang, A., Shelton, J. R., Urbach, F. L., Dunbar, R. C., and Kopczeuski, R. F., J. CHEM.EDuC., 53,394 (1976). Wasson, J. R., horg. Chem., 10, 153 (1971). Yen. Teh Fu. "Electron Spin Resonance of Metal Complexes," Plenum Press, New York. 1969. Wasson, J. R., et al., J. horg. NUCI. Chem., 36, 1184 (1974). Wasson, J. R., e t al., J. Phys. Chem., 78, 962 (1974).
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Londa L. Borer California State University-Sacramento Sacramento. CA 95819
Volume 5 9
Number 1 2
December 1982
1065
