Infrared Absorption Spectra of Inorganic Coördination Complexes. VII. Structural Isomerism of Nitro- and Nitritopentamminecobalt(III) Chlorides^1a,b

Abstract

Infrared spectra of nitropentamminecobalt(III) chloride and mtritopentamminecobalt(III) chloride in the solid state have been measured. Spectral evidence is presented to support the conversion of nitritopentamminecobalt(III) chloride to nitropentamminecobalt(III) chloride. In the spectra of these complexes the deformation vibration frequencies of the NH3 ligand, degenerate, symmetric and rocking are identified. The remaining absorption bands in the region from 1700 to 650 cm.-1 (5.8-15 µ) can be assigned to the nitro and nitrito frequencies. Changes in the spectrum of the nitritopentamminecobalt(III) ion with regard to intensity of certain bands with time are significant. Bands which show such changes in absorption are assigned to those parts of the complex which are responsible for nitrito and nitro vibrations. By comparison of the spectra of the pure nitro and the freshly prepared nitrito isomers, the bands that decrease in intensity can be assigned to the nitrito group, while those new bands that appear and gradually increase in intensity can be assigned to the nitro group.

Infrared and Raman Spectroscopic Studies of Solid Alkali Metal Nitrites

“…49,1971 merely to suggest that the band at 872 cm-' is associated with a nitrite site with short Li-0 distances; whereas the band at 842 cm-I is associated with a nitrite site with short Li-N distances. If a strongly covalent nitrito linkage was actually present (as in nitrito complexes of cobalt), one would anticipate a decrease in the symmetric stretching frequency (41)(42)(43); in fact, the symmetric stretching frequency does not shift. In the hydrate, only one band is present in the deformation region which would indicate that the nitrite ions lie on a single site.…”

Coordination chemistry II: stereochemistry

“…Dissolve the precipitate in absolute ethanol (30 cm 3 ) to which water (0'5 cm 3 ) has been added, cool in ice. Dissolve the precipitate in absolute ethanol (30 cm 3 ) to which water (0'5 cm 3 ) has been added, cool in ice.…”

“…(1) Geometrical isomerism (2) Optical isomerism (3) Ionization isomerism (4) Hydrate isomerism (5) Coordination isomerism (6) Linkage isomerism.…”

“…This reaction must be carried Ollt in a fllme Clipboard.Cool 300 cm3 of ether in ice and saturate it with hydrogen chloride. Dissolve dichlorotetraquachromium(III) chloride (14 g) in water (20 cm 3 ), and reflux for ten minutes.…”

“…Materials required: Cobalt(I1) carbonate 6% Hydrogen peroxide (20 volume) Aqueous ammonia (S.G. 0·88) Dissolve cobalt(II) carbonate (S g) in concentrated hydrochloric acid (15 cm 3 ), add water (35 cm3 ) and filter to remove any undissolved oxide which was present in the original carbonate. To this solution add ammonium chloride (5 g) and 50 cm 3 of aqueous ammonia (S.G. 0·88).…”