CD-113 SHIELDING TENSORS OF CADMIUM COMPOUNDS .8. SOLID-STATE CD-113 NMR-STUDIES OF POLY(BIS(GLYCINE)CADMIUM CHLORIDE)

The Cd-113 shielding tensor of the cadmium compound poly(bis(glycine)cadmium chloride) has been determined via powder and single-crystal solid-state NMR experiments. The isotropic chemical shift determined was 115 ppm, and the individual shielding tensor components obtained through single crystal methods are sigma(11) = 263.0 +/- 0.4 ppm, sigma(22) = 196.0 +/- 2.0 ppm, and sigma(33) = -111.0 +/- 3.6 ppm. The spatial arrangement of the molecules in the crystal lattice generates two magnetically distinguishable tensors. The coordination about the cadmium metal ion is a distorted octahedron and can be described in terms of three molecular planes. By the use of these planes, the ligand contribution to the Cd-113 nuclear shielding could be predicted by the progression in the direction of lower shielding of the best least-squares planes of atoms: O-O-O-Cl > O-O-Cl-Cl > O-Cl-Cl-Cl. Here O represents a carboxylate oxygen from glycine and Cl a chloride ion. Generally, chlorides are more deshielding ligands of cadmium than are carboxylate oxygens. On the basis of this assessment and a collection of single-crystal experimental observations on cadmium compounds, an assignment of the Cd-113 shielding tensor to the appropriate lattice site was accomplished. The most shielded tensor element, sigma(33), is oriented nearly perpendicular to the most shielding best least-squares plane defined by three oxygens and one chloride. The most deshielding tensor element is aligned mostly perpendicular to the most deshielding best least-square plane defined by three chlorides and one oxygen. The sigma(22) component is most perpendicular to the plane defined by two chlorides and two oxygens.