The chemical identity of “[Ag(py)2]MnO4” organic solvent soluble oxidizing agent and new synthetic routes for the preparation of [Ag(py)n]XO4 (X = Mn, Cl, and Re, n = 2–4) complexes

Abstract

A widely used oxidizing agent in organic chemistry with an assumed structure of “[Ag(py)2]MnO4” and its perchlorate and perrhenate analogues are studied. Their synthesis in pure form is challenging. In order to clarify the chemical nature of the known compounds and find routes to new derivatives, a systematic study is presented for the synthesis of [Ag(py)n]XO4 (X = Mn, Cl, and Re, n = 2–4) complexes. Ten complexes including four new derivatives, [Ag(py)4]MnO4, [Ag(py)4]MnO4·4[Ag(py)2]MnO4, [Ag(py)2]ClO4·0.5 py, and [Ag(py)2]ReO4, are synthesized and characterized. The chemical identity of “Ag(py)2MnO4” is also clarified. A novel route to prepare [Ag(py)2]MnO4 is developed. The reaction of AgXO4 salts with neat pyridine followed by various crystallization techniques is used to prepare [Ag(py)2]XO4, [Ag(py)4]XO4, [Ag(py)4]XO4·4[Ag(py)2]XO4, and [Ag(py)2]XO4·0.5py (X = Cl, Mn) complexes. The solid phase structure of [Ag(py)2]MnO4·0.5py is determined (a = 19.410 Å, b = 7.788 Å, c = 21.177 Å, β = 104.20°, C2/c (15), Z = 4 (3a)). [Ag(py)2]+ cations in the crystal form dimeric units where silver ions are connected by oxygen atoms of two MnO4 – anions. The Ag…Ag distance is indicative of argentophilic interactions. The pyridine ring π…π interactions contribute to the stability of the crystal lattice.