Polymorphism and tautomerism in [dienH2][Co(dien)2][Ge2S6] leading to different hydrogen bonded networks

Abstract

Four compounds of composition [dienH₂][Co(dien)₂][Ge₂S₆] (dien = diethylenetriamine) were obtained under solvothermal conditions changing the reaction time and educt ratio in the reaction slurries. In three compounds the [Co(dien)₂]²⁺ complexes adopt the s-fac and in one the u-fac configuration. The main differences between the samples are found in the number and type of protonated dien molecules. In one distinct cation of compound 1 as well as in compound 2 the terminal N atoms are protonated, whereas in the second cation of 1 as well as in 3 and 4, one terminal and the central N atom are protonated. Therefore, the compounds with different protonated cations are tautomers, whereas compounds 3 and 4 represent polymorphic modifications. The occurrence of tautomerism and polymorphism for compounds with identical chemical composition is unprecedented in the chemistry of thiometallates and was never reported until now. In the crystal structure of all compounds the (dienH₂)²⁺ cations and the [Ge₂S₆]⁴⁻ anions are linked by intermolecular N–H⋯S hydrogen bonding into different supramolecular networks.