Nitration of Metal Ion Coordinated Imidazole and the Crystal Structure of Pentaammine (4-nitroimidazolato)cobalt(III)chloride

The title complex, [Co(NH 3) 5(NO 2Im)]Cl 2, was prepared by the action of a standard HNO 3-H 2SO 4 nitrating mixture on Co(NH 3) 5(ImH) 3+. The complex has been characterized by 1H NMR and UV-vis spectroscopy and a single-crystal X-ray structure determination. The pH dependence of the 1H NMR spectra has been determined, and the pK a of the coordinated NO 2Im is 1.66. Crystal data for [Co(NH 3) 5(NO 2Im)]Cl 2 is as follows: space group P2 1/n; Z = 4; a = 9.434 (2), b = 13.679 (3), c = 10.457 (3) Å; β = 93.65 (2)°; V= 1346.7 (5) Å 3; R = 4.5% for 2135 reflections. © 1983 American Chemical Society