CD-113 SHIELDING TENSORS OF CADMIUM COMPOUNDS .5. SINGLE-CRYSTAL STUDIES OF THE DIMER OF DIAQUOBIS(2-HYDROXYBENZOATO)CADMIUM(II) AND TETRAKIS(4-PICOLINE)(NITRATO-O,O')(NITRATO-O)CADMIUM(II)

The orientation of the 113Cd chemical shielding tensors in single crystals of the dimer of diaquobis(2-hydroxybenzoato)cadmium(II), i.e. Cd-salicylate, and tetrakis(4-picoline)(nitrato-O,O′) (nitrato-O)cadmium(II), i.e. Cd-picoline, has been determined. The isotropic chemical shift was determined to be −31 ppm for Cd-salicylate and +11′ ppm for Cd-picoline. The space group symmetry of the Cd-salicylate crystal generates two magnetically distinct cadmium lattice sites. The assignment of each experimentally determined tensor to its respective lattice site was not possible due to the special geometry of the ligands in the lattice, which is discussed in the text. However, the two possible orientations differ only slightly and it is therefore possible to interpret the orientation with respect to the ligand identity and geometry. In either case, the most deshielded element is oriented nearly perpendicular to a plane containing two water oxygen atoms. The most shielded element is oriented nearly perpendicular to a pentagonal best least-squares (BLS) plane defined by two pairs of bidentate benzoate oxygen atoms and one monodentate benzoate oxygen atom. The crystal of Cd-picoline generates two crystallographically distinct cadmium sites in the lattice. Two methods were used independently to assign the two experimentally determined tensors to each lattice site. The first method utilizes the empirical observations of shielding contributions of nitrogen versus oxygen ligand donors. The second method exploits the angular dependence of the line width as a function of rotation angle due to dipolar coupling between the spin I = ½ 113Cd nucleus and the spin I = 1 14N nuclei. The two methods consistently assign each tensor to a respective lattice site. At each lattice site, the most deshielded tensor element is oriented nearly orthogonal to a BLS plane of nitrogen atoms defined by four monodentate picoline ligands. Also, at each lattice site, the most shielded element is nearly perpendicular to a plane defined by the Cd2+ ion and the two bidentate nitrate oxygen atoms. © 1990, American Chemical Society. All rights reserved.