ZEEMAN EFFECT OF CL-35 NQR IN PERCHLORO-5-METHYLCYCLOPENTADIENE

Perchloro-5-methylcyclopentadiene gives five NQR lines at 77 K: v1 = 40.769, v2 = 39.761, v3 = 39.433, v4 = 37.905, and v5 = 37.086 MHz, all without fading out below its mp, 366 K. The Zeeman spectrum of this compound revealed that the crystal exhibits an orthorhombic lattice with the mm2 or mmm symmetry and that the principal Z axes of efg tensors for v2 and v3 are parallel to each other. The signal assignments for v2 and v3 were made by comparison of their S N ratios at 365 K. The lines v1 and v3 were assigned to the CCl3 group. The crystal and molecular structures were discussed on the basis of the results of the Zeeman-effect analyses. The frequency difference (ca. 1.3 MHz) between v1 and v3 was interpreted in terms of homohyperconjugation" and a transannular interaction of the chlorine atom corresponding to v3 with the diene system. © 1978."