Cd-113 shielding tensors of monomeric cadmium compounds containing nitrogen donor atoms .3. CP/MAS studies on five-coordinate cadmium complexes having N(3)X(2) (X=H,N,O, and S) donor atoms

The principal elements of the Cd-113 shielding tensor for a set of five- coordinate compounds having mixed donor atoms coordinating to the cadmium were determined via CP/MAS NMR experiments. The first complex, [HB(3,5-Me(2)pz)(3)]CdBH4 (where pz = pyrazolyl), has a CdN3H2 inner coordination sphere. The isotropic chemical shift in the solid state is 355.1 ppm, and its chemical shift anisotropy (CSA, Delta sigma) is -596,ppm with an asymmetry parameter (eta) of 0.64. The second complex, [HB(3,5-Me(2)pz)(3)]Cd[H2B(pz)(2)], has five nitrogen donor atoms bonded to the cadmium. This N-5 or N3N2 compound was the only material of this study to manifest dipolar splitting of the cadmium resonance from the quadrupolar(14)N. Th, isotropic chemical shift, CSA, and the value of eta for this material were therefore determined at higher field where the dipolar splitting was less than the linewidth, yielding values of 226.6 ppm, -247 ppm, and 0.32, respectively. A second N-5 material, [HB(3-Phpz)(3)]Cd[H2B(3,5-Me(2)-pz)(2)], was also investigated and has an isotropic shift of 190.2 ppm, a CSA of 254 ppm, and an eta of 0.86. Also studied was [HB(3-Phpz)(3)]Cd[(Bu(t)CO)(2)CH], which has an CdN3O2 inner core. The isotropic chemical shift of this complex is 173.6 ppm, and the values of Delta sigma and eta were determined to be -258 ppm and 0.38, respectively. The final compound, [HB(3,5-Me(2)pz)(3)]Cd[S(2)CNEt(2)], with N3S2 donor atoms, has an isotropic shift of 275.8 ppm, an eta of 0.51, and a CSA of +375 ppm. Utilizing previous assignments, the most shielded tensor element was determined to be oriented normal to the plane of the tridentate ligand. The shielding tensor information is used to speculate on the Coordination geometry of the CdN3O2 inner core complex.