A 2D deuterium NMR study of molecular reorientation in (CH3)(3)E+X- onium salts

Two dimensional deuterium NMR measurements are reported for three different onium salts (CH3)(3)SeNO3-d(3), (CH3)(3)TeI-d(3), and (CH3)(3)SI-d(9). In these molecular solids with the general structure (CH3)(3)E+X-, three methy l groups are attached to the E atom. There is the possibility of reorientat ion of the methyls about their C-3 axes and reorientation of the whole tri- methyl group about the C-3' axis. From an analysis of the 2D NMR exchange s pectra the angle between the E-C bonds and the rotation axis for trimethyl reorientation were determined. Exchange rates and spin lattice relaxation t imes are given for several temperatures, to show how the mixing times for t he experiments were selected. The data presented for (CH3)(3)TeI-d(3), demo nstrate that 2D techniques are sensitive to motions on a time scale an orde r of magnitude slower than that accessible using ID line shape techniques.