Inorg. Chem. 1992, 31, 1965-1968 Table 111. ESR Data for Suin-Coupled Dimeric Vanadyl Complexes ampd gll A,,, cm-l 1.95 0.0074 (Bu,N),[(VO),(DcP)zl 0.007 23 Na,[VO(d,l-tartrate)] 2H20 1.953 0.007 32 Na4[VO(d-tartrate)I2-6H20 1.950 1.967 0.00771 5 [VO(TCP)l2(K+)4
1965
A,,
g,
1.98 1.982 1.984 1.987
cm-'
D, cm-' 0.0343 0.0334
0.0038 0.00213 0.00246 0.00259 8
0.0335 0.02685 0.02610
ref this work 3a 3a 3e
I
ImO
moa
won
um
5mO
bmn
mar lC.ur)
Figure 3. ESR spectrum of the ( B U ~ N ) ~ [ ( V O ) ~complex D C ~ ~ at ] 93 K in acetone/2-propanol/methanol (1 5:4:1)glass. Inset shows expanded AMs f 2 transition.
protonation of the ligand, which precipitated from solution. A similar result was noted for hydrogen peroxide. The complex appears to lose its integrity upon oxidation and does not facilitate the formation of a peroxo adduct. I Acknowledgment. P.G.R. acknowledges support from the do2500 2750 3000 3250 3500 3750 4000 4250 ,4500 nors of the Petroleum Research Fund, administered by the AmFIELD I N GRUSS erican Chemical Society. J.C.B. acknowledges support from the Spanish DGICYT Project PB88-0252. C.W.H. acknowledges Figure 2. (A) Room-temperature ESR spectrum of (Bu4N)2[(VO),(Dcp),] in acetone. (B) Simulated ESR spectrum for (BU~N)~[(VO)~- support from undergraduate research funds of the College of Literature, Science and the Arts. The assistance of Dr. Jeffrey (Dcp),] using g = 1.97and A = 50.44 X IO4 cm-' (line width = 53 G). Kampf, X-ray crystallographer of the Department of Chemistry The isotropic g and A values are from the isotropic room-temfor data collection, is gratefully acknowledged. perature spectrum. The resulting parameters are compared with Supplementary Material Available: Tables of thermal parameters, those of related vanadium dimers in Table 111. bond lengths, bond angles, and crystallographicdata (8 pages); a listing The pointdipole approximation for an axially symmetric system of structure factors (24 pages). Ordering information is given on any may be used to confirm the value of the zero-field-splitting pacurrent masthead page. rameter?a Using the crystallographically determined V-V distance (4.206 A) and the gvalues gives calculated zero-field values of D = 0.0332 cm-l and D = 0.0342 cm-'for glland g, respectively. These values are in very good agreement with the value of D = 0.0343 cm-' extracted from the spectrum. The electronic spectrum for (BU,N)~[(VO)~(DC~)~] shows the Contribution from the Department of Chemistry, three optical bands expected for a vanadyl complex. The asTulane University, New Orleans, Louisiana 701 18 signments of the bands for the complex follow the Ballhawen and Gray model for the one-electron transitions d, d,,,d,,, d -, Conversion of Chlorofluorocarbons into dx2-,,2,and d dZz,respectively.I0 The bands occur at 609 nm Chlorofluorohydrocarbns Using the Atherton-Todd Reaction (e = 8.21 cm-I), 530 nm (e = 10.01 cm-I), and 431 nm (e = 7.21 with Dimethyl Phosphonate cm-I), respectively. The energy of the third band shows that the vanadyl remains five-coordinate in solution, as axial coordination Emil Georgiev, D. Max Roundhill,' and Koljo Troevl of a sixth ligand would cause it to occur at
