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2629previously reported2' an interesting selective behavior of V-silicalite in propane oxidative dehydrogenation to propylene. The formation of this activated oxygen species and, more generally, the presence of stabilized tetrahedral Vs+ sites may thus be the key factor in explaining the peculiar catalytic characteristics of V-silicalite, especially in alkane oxidative dehydrogenation. Further studies are in progress to clarify this aspect. However, it should be noted that the number of V5+ sites which appear to be stabilized in defect site position is rather low, which certainly affects the activity of the V-silicalite and its possible applications. Alternative methods may enhance their amount and the catalytic performance of this system, which appears to be rather interesting, especially for the possibility of having isolated stabilized tetrahedral Vs+ sites with a redox character.The sensitivity of the solid-state deuterium NMR line shape to the motion of the C-D bond is exploited to investigate the state of phenanthrene-d,, in zeolites with various counterions. NMR line-shape analysis and measurement of the relaxation time of the Zeeman order (TI) support the existence of two independent spin reservoirs. Spectral line shapes are decomposed into contributions from each spin reservoir to determine equilibrium constants for ion-phenanthrene association as a function of temperature. AH for this process decreases with increasing cation radius. IntroductionZeolites are crystalline aluminosilicate materials with open framework structures' that find applications in catalysis, separations, detergent formulations, and, more recently, as a medium for studying photochemistry.2 The two synthetic forms of fau-

The NMR properties of the solid lead (II) halides and the lead (II) hydroxyhalides are reported. The analysis shows extremely wide powder patterns in all cases except the lead (II) iodide. The results indicate that one should be able to distinguish the lead (II) halide from the corresponding lead (II) hydroxyhalide in a mixture.