ELECTRON MAGNETIC RESONANCE OF ORIENTED VANADYL IONS IN SINGLE CRYSTALS OF PALLADIUM TRANS-BIS(BENZOYLACETONATE) AND ZINC CIS-BIS(BENZOYLACETONATE) ETHANOLATE

Successful preparation and electron paramagnetic resonance of vanadyl ions (VO2+) substituted in unique orientations into single crystals of palladium trans-bis(benzoylacetonate) and zinc cis-bis(benzoylacetonate) ethanolate are described. There is circumstantial evidence that the species studied are the cis and trans forms of vanadyl bis(benzoylacetonate), of which only the cis isomer was previously known. The orientations of the principal axes of the g tensors suggest that each vanadyl complex is tilted relative to the corresponding host molecule; in the palladium lattice this rotation is such as to move the vanadyl oxygen atom directly away from a neighboring methyl group. The bonding parameters estimated from these data indicate that the π-type orbitals dx2-y2, dxz, and dyz are fairly ionic and that the σ-type orbital, dxy, is significantly more covalent. The electronic spectrum of the vanadyl ion could not be measured in the Pd lattice, but in the Zn lattice band maxima occurred at 12,700, 16,300, and 20,800 cm-1. If the band at 12,700 cm-1 is derived from the transitions dx2-y2 → dxz and that at 16,300 cm-1 is from dx2-y2 → dxy the epr measurements are most easily interpreted. The g values of the vanadyl complex in the palladium lattice suggest a similar ordering of the excited states. The in-plane g and hyperfine anisotropy observed for each complex can be explained adequately by a slight admixture of d3d2 into the ground state, and the sign of the mixing coefficient suggests that the presence of the chelate rings perturbs the ground-state orbital of the metal ion in the same sense as would negative charges on the internal bisector of the chelate rings. © 1969, American Chemical Society. All rights reserved.