Erdmann’s Anion—An Inexpensive and Useful Species for the Crystallization of Illicit Drugs after Street Confiscations

Erdmann’s anion [1,6-diammino tetranitrocobaltate(III)] is useful in the isolation and crystallization of recently confiscated street drugs needing to be identified and catalogued. The protonated form of such drugs forms excellent crystals with that anion; moreover, Erdmann’s salts are considerably less expensive than the classically used AuCl₄⁻ anion to isolate them, while preparation of high-quality crystals is equally easy in both cases. We describe the preparation and structures of the K⁺CoH₆N₆O₈⁻ and NH₄⁺CoH₆N₇O₈ −_, salts of Erdmann’s. In addition, herein are described the preparations of this anion’s salts with cocaine (C₁₇H₂₈CoN₇O₁₂), with methamphetamine (C₁₀H₂₂CoN₇O₈), and with methylone (C₂₂H₃₄CoN₈O₁₄), whose preparation and stereochemistry had been characterized by the old AuCl₄⁻ salts methodology. For all species in this report, the space groups and cell constants were determined at 296 and 100 K, looking for possible thermally induced polymorphism—none was found. Since the structures were essentially identical at the two temperatures studied, we discuss only the 100 K results. Complete spheres of data accessible to a Bruker ApexII diffractometer with Cu–Kα radiation, λ = 1.54178 Å, were recorded and used in the refinements. Using the refined single crystal structural data for the street drugs, we computed their X-ray powder diffraction patterns, which are beneficial as quick identification standards in law enforcement work.