Synthesis of an organo-hexachlorostannate hybrid compound: A case of a bridged tricyclic organic hydrochloric salt stabilized by the packing in its crystal structure

The use of 2-aminopyrazine in preparing organo-hexachlorostannates compounds has not been reported. Literature shows few reports related to the functionalization of this aromatic ring, indicating that the chemistry associated with this compound has not been sufficiently explored. In this work, a new organo-hexachlorostannate (OHcs) compound has been isolated using a simple experimental protocol dissolving SnCl₂^.2H₂O in concentrated hydrochloric acid. This compound is described as an isolated octahedra hexachlorostannate [SnCl₆]^2- anion conforming the crystal structure with the organic moiety 3,7-diamino-1,2,4a,5,8,8a-hexahydro-8,5-(epiminomethano)pyrido[3,4-b]pyrazin-10-ol which is present in its multi-protonated hydrochloric salt form. X ray diffraction analysis was performed to determine the structure of crystals grown by slow evaporation after the reaction process. Additionally, infrared spectroscopy (IR), high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DCS) techniques were used to characterize the product. Considering the lack of reports in the literature, this work concludes that this compound is only stable in the solid state due to packing stabilization. However, a reversible reaction favoring the formation of 2-aminopyrazine hydrochloride takes place in solution. Following the results from these experiments, we propose that this organo-hexachlorostannate hybrid compound is formed through a multi-step synthesis via Stephen reduction and an inverse electron demand Diels-Alder (IEDDA) cycloaddition which opens interesting alternatives to synthesize new polycyclic compounds.