NUCLEAR QUADRUPOLE RESONANCE ZEEMAN STUDY OF POLYCRYSTALLINE GROUP 4A TETRACHLORIDES

The asymmetry parameters of the electric field gradients at the chlorine nuclei in four group IVa tetrachlorides have been determined by employing a polycrystalline Zeeman analysis of their nuclear quadrupole resonance transitions. The parameters found were: CCl4 (<0.10), SiCl4 (0.45), GeCl4 (0.35), and SnCl4 (0.25). The magnitudes of these parameters for the latter three compounds are larger than can be rationalized on the basis of intermolecular bonding alone. It is believed that these large values provide additional evidence for the existence of dπ-pπ bonding in these compounds.