Brown Nitrosylpentamminechromium(III) Salts and Green Nitrosylpentamminechromium(III) Perchlorate

A new series of chromium ammines, i.e., nitrosylpentamminechromium(III) salts, were obtained by the reaction of an ammoniacal chromium(II) solution with sodium nitrite. The derivatives are usually reddish brown, but only the perchlorate is bright green. The infrared absorption spectra indicate that in the green perchlorate the rocking frequency of ligating ammonia is lower, while the stretching frequency of the nitrosyl group is higher than in the brown chloride. These results seem to show indirectly that the coordinate linkage is weaker in the green perchlorate.