HIGH-RESOLUTION CD-113 MAS NMR INVESTIGATION OF STRUCTURE AND BONDING IN CADMIUM THIOCYANATE COORDINATION-COMPOUNDS - DISTANCE DEPENDENCE OF CADMIUM NITROGEN INDIRECT SPIN-SPIN COUPLING-CONSTANTS

A number of cadmium thiocyanate complexes of varying stoichiometry (1:2, 1:3, 1:4) have been prepared and investigated by solid-state Cd-113 MAS NMR spectroscopy. The application of this technique in characterizing the various modes of linkage isomerism exhibited by the ambidentate thiocyanate ligand is discussed in detail. The Cd-113 isotropic chemical shifts and chemical shift anisotropies provide information concerning the coordination number of cadmium in these complexes. For the octahedral complexes, the Cd-113 isotropic chemical shifts span a range of 213 ppm with the Cd(NCS)6 fragment being most shielded (delta(iso) = 130.0 ppm) and the Cd(SCN)6 fragment being least shielded (delta(iso) = 342.9 ppm). Each distinct cadmium site in the cadmium thiocyanates exhibits multiplets that result from Cd-113, N-14 spin-spin coupling. Analysis of these multiplets reveals the number of nitrogen atoms attached to cadmium. The magnitudes of the indirect Cd-113, N-14 spin-spin coupling constants in these complexes vary from 37 to 178 Hz and appear to be related to the cadmium-nitrogen separation.