CD-113 SHIELDING TENSORS OF MONOMERIC CADMIUM COMPOUNDS CONTAINING NITROGEN DONOR ATOMS .2. SYNTHESES, CRYSTAL-STRUCTURES, AND CD-113 NMR-SPECTROSCOPY OF THE 6-COORDINATE COMPLEXES [HB(PZ)(3)]2CD, [HB(3-PHPZ)(3)]2CD, AND [B(PZ)(4)]CD[HB(3-PHPZ)(3)] (PZ=PYRAZOLYL)

All possible mixed-ligand complexes of the formula LL'Cd (L, L' = [HB( pz)(3)](-), [HB(3,5-Me(2)pz)(3)](-), [B(pz)(4)](-), [HB(3-Phpz)(3)](-) (pz = pyrazolyl)) were prepared by the reaction of a 1/1/1 molar rati o of the desired ligand salts and CdCl2. The new symmetrical complex [ HB(3-Phz)(3)]Cd-2 was prepared from 2 equiv of the ligand salt and CdC l2. The solid state structures of [HB(pz)(3)]Cd-2 (1), [HB(3-Phpz)(3)] Cd-2 (4), and [B(pz)(4)]Cd[HB(3-Phpz)(3)] (10) have been characterized by X-ray crystallography. All three are pseudo-octahedral, but the st ructures of both 4 and 10 are distorted by a rotational movement of on e ligand relative to the other ligand. Because of this rotation with 4 and 10, the trans N-Cd-N bond angles are significantly distorted from 180 degrees, leading to one set of cis, interligand N-Cd-N angles tha t average 89.3 and 92.4 degrees and another that average 100.6 and 105 .7 degrees, respectively. The Cd-N bond distances (average 2.33 Angstr om) for 1 are similar to those observed earlier in the structures of [ HB(3,5-Me(2)pz)(3)]Cd-2, [B(pz)(4)](2)nCd and [B(3-Mepz)(4)]Cd-2, but the Cd-N distances are longer in 4 (average 2.39 Angstrom) and in 10 ( [HB(3-Phpz)(3)](-) ligand average 2.39 Angstrom and the [B(pz)(4)](-) ligand 2.36 Angstrom. The solution Cd-113 NMR chemical shifts for comp lexes containing the [HB(Phpz)(3)](-) are substantially more shielded than the other complexes in the series. A regression analysis of the s olution Cd-113 NMR chemical shifts for all of these complexes for the shift caused by each ligand relative to Cd(ClO4)(2) shows a good corre lation of the calculated and observed chemical shifts of these complex es. These shift values (ligand/ligand shift, delta) are [HB(pz)(3)](-) /97.3, [HB(3,5-Me(2)pz)(3)](-)/101.7, [B(pz)(4)(])-/107.4, and [HB(3-P hpz)(3)](-)/44.9. The principal components of the Cd-113 shielding ten ser were determined from CP/MAS data. The sigma(33) element was found to be relatively independent of the Cd-N bond hlgths while the opposit e is true of sigma(11). This accounts for the dependence of the shield ing anisotropies upon the bond distances. The respective chemical shif t anisotropies and asymmetry parameters for 1 (both line shapes), 4, a nd i10 are -238.7, -228.4, -138.5, and -220.8 ppm and 0.55, 0.65, 0.26 , and 0.15 ppm.