Reasons for and Consequences of the Mysterious Behaviour of Newly Prepared Hemipyridine Solvate of Bis(pyridine)silver(I) Permanganate, Agpy2MnO4*0.5py

Compositions and chemical identities of compounds formed in silver–permanganate–pyridine–water systems, as well as of their recrystallization products obtained from benzene–acetone solutions, have been elucidated. Three compounds: Agpy2MnO4 (1), 7Agpy2MnO4*Agpy4MnO4 (Agpy2.25MnO4) (2) and Agpy2MnO4 * 0.5py (Agpy2.5MnO4) (3) were isolated. The compositions of the products obtained by a method described previously [1] for the preparation of ‘Agpy2MnO4’ (1*) and ‘Agpy2.5MnO4’ (2*) were determined and the constituent compounds identified. It has been established that the instability of compound (3) is due to the presence of the benzene, substituting for pyridine at the solvate sites. The benzene, however, is released at room temperature, disrupting the crystal lattice of (3), and the whole process leads to the loss of the solvate pyridine and to the formation of (1).