Tin-chlorine coupling in magic-angle spinning N.M.R. spectra

Abstract
Perturbation theory is developed to describe magic-angle spinning (MAS) N.M.R. spectra of spin-1/2 nuclei scalar coupled to spin-3/2 nuclei under conditions where second-order effects are important. It is shown that information on indirect coupling (including its anisotropy), dipolar interactions and quadrupolar coupling is contained in the spectra. The concepts are extended to situations where two equivalent quadrupolar nuclei are involved. Examples from tin-chlorine chemistry are presented and discussed. Tin-119 spectra of bis (acetylacetonato)tin(IV)-dichloride were obtained at two different magnetic fields. It is concluded that the isotropic coupling constant |J(Sn, Cl)| is 276 Hz and the tin chemical shift in the solid state is -642·2 ppm (relative to the signal for tetramethyltin). Values of the anisotropy in indirect (Sn, Cl) coupling, ΔJ, are suggested for several compounds to lie in the range -400 to -800 Hz.