Vanadium in minerals

E.p.r. studies459 indicate the formation of sandwich-type dimer complexes of V02+ and etioporphyrin (EP) in light petroleum at 77 K the e.p.r. data are consistent with an EP-EP plane distance of ca. 3.5 A. A planar ligand local environment for Vlv, possibly provided by a phthalocyanine- or porphyrin-type ligand, has been proposed460 to account for the axial microsymmetry of the V17 centre and the absence of zero-field splitting indicated by e.p.r. studies of vanadium in mineral oil. 

Vanadium, in Mineral Facts and Problems, Bull. 671, U.S. Bureau of Mines, Washington, D.C., 1980. 

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