The Properties of the Hexanitro Complexes of Divalent Iron, Cobalt, Nickel, and Copper

Abstract

The X-ray powder photographs, magnetic susceptibilities, infrared spectra, electronic spectra (as reflectance), and electronspin resonance spectra of nine hexanitro complexes of divalent iron, cobalt, nickel, and copper are reported. They are of the form KsM'tM'XNOah] where M" is a divalent transition metal ion and M' is a divalent cation (lead or barium, and, in the case of the copper complex, calcium). All the complexes were confirmed as having face-centered cubic crystal structures except for the barium-copper and the calcium-copper complexes, which were shown to be weakly tetragonal. The unit cell dimension a of the cubic lead complexes shows a systematic increase from iron to copper corresponding to an increase in the metal to nitrogen distance in this sequence, consistent with the increasing repulsion experienced by the ligands as electrons are added to the eg orbitals. The electronic reflectance spectra of the iron and nickel complexes are consistent with a regular octahedral coordination and a crystal field splitting of 13,590 cm-1 is indicated for the nickel complex, the highest value yet reported for a spin-free octahedral nickel(II) complex. The electronic spectra of the cobalt and copper complexes closely resemble one another and are only consistent with a tetragonal environment for the transition metal ions. The observation of an isotropic electron spin resonance spectrum for the lead-copper, the lead-cobalt, and the barium-cobalt complexes, but an anisotropic spectrum for the barium-copper and calcium-copper complexes, suggests that the former complexes may be undergoing a dynamic Jahn-Teller distortion.

Crystal structures, magnetic properties and DFT study of cobalt(II) azido complexes with the condensation product of 2-quinolinecarboxaldehyde and Girard’s T reagent

“…DFT calculated g-values for Co(II) complex 1 are summarized in Table 3. These results are similar to those reported for low-spin octahedral Co(II) complexes [33,36,43,52].…”

Base adducts of .beta.-ketoenolates. VI. Single-crystal electron paramagnetic resonance and optical studies of copper(II)-doped cis-bis(hexafluoroacetylacetonato)bis(pyridine)zinc(II), Cu-Zn(F6acac)2(py)2

“…Although the properties of Cu-Zn(F6acac)2(py)2 between 4.2 and 133°K have not been studied, the variation of the g values with temperature can be predicted from the g values of the three static configurations at low temperature by assuming that two processes occur as the temperature is raised: (1) an averaging of the two equivalent configurations to only one line at £<V +gs)l2 ( 4) and (2) a mixing of configuration 1 with the average obtained above to a final line at g = bgázi +(1 ~b)gi (5) If we express the g tensors of the static complexes in a coordinate system given by the principal directions of the g tensor found at high temperature, we get on averaging g'\\=bg'z{2) + (1 -b)g'z( 1) g'± = bg'x,y(2) +(1 ~b)g'Xiy(l)…”

Infrared and Raman studies of nitrate impurity in nitrite complexes

“…The presence of solid sodium brómate in the reaction mixture improves the yield of perbromate with respect to fluorine consigned, probably by maintaining saturation as the reaction proceeds. (5) Although most of the fluorine is absorbed by the báse, enough escapes to make it imperative that the reaction be carried out in a well-ventilated fume hood. The reaction is not smooth, and small explosions may take place in the vapor above the solution.…”