Nuclear quadrupole resonance in a single crystal of dimethyltin dichloride

The Zeeman NQR spectrum of a single crystal of dimethyltin dichloride has been reinvestigated in view of an improved determination of the crystal structure. The study shows the existence of two zero-splitting loci for the chlorine atoms. The quadrupole coupling constant was found to be ?30.92 MHz with an asymmetry parameter of η = 0.32. The principal EFG Z-axes are coincidental with the SnCl bonds, the Y-axes parallel to the crystallographic b-axis and the X-axes lie in the cb-plane. Using the Townes Dailey theory the fraction of π-bonding was calculated to be 0.24 with π_y-π_x = ?0.06. The imbalance in the π-bonding is rationalized on the basis of d-p overlap between the chlorine p_y-orbitals and the tin d-orbitals.