Structural organization of cadmium(II) and copper(II) dithiocarbamate complexes with dialkyl-substituted and cyclic ligands:: Synthesis, single-crystal X-ray diffraction, EPR, and CP/MAS 13C, 15N, and 113Cd NMR

The structures and spectral properties of cadmium and copper(II) dithiocarbamate complexes with the general composition [M-2(S2CNR2)(4)] (M = Cd, Cu-63, Cu-65; R = C2H5, C3H7, i-C3H7, C4H9, i-C4H9; R-2 = (CH2)(6)) were studied by multinuclear MAS NMR (C-13, N-15, Cd-113) and EPR. The cadmium dipropyldithiocarbamate complex [Cd-2{S2CN(C3H7)(2)}(4)] was synthesized, and its single crystal was studied in detail by X-ray diffraction at 173 K. This binuclear molecule is centrosymmetric, and its central eight-membered tricyclic moiety [Cd2S4C2] has a chair conformation. The experimental N-15 and 13 C NMR signals were assigned to the positions of the corresponding atoms in the dithiocarbamate groups of the ligands with different structural functions, i.e., of the ligands coordinated in the bidentate terminal or bridging/terminal mode. The differences in the N-15 isotropic chemical shifts of the dialkyldithiocarbamate ligands were interpreted based on the concept of joint manifestation of the mesomeric effect of the dithiocarbamate groups and the inductive effect of the alkyl substituents. Constructing the chi(2) plots allowed us to quantitatively characterize the Cd-113 chemical shift anisotropy: the chemical shift anisotropy (delta(aniso) = delta(zz) - delta(iso)) and asymmetry parameter (eta = (delta(yy) - delta(xx))/(delta(zz) - delta(iso))) were calculated. EPR showed that copper(II) in the complexes magnetically diluted with cadmium is mainly in tetragonal-pyramidal coordination polyhedra somewhat distorted toward a trigonal bipyrarnid. In addition, it was found that, in magnetically diluted systems, copper(II) can form mononuclear square-planar complexes [Cu(S2CNR2)(2)].