An unusually water-poor 5,50-azobistetrazolate of dysprosium: stabilization of a nitrogen-rich heterocycle by a minimum of hydrogen bonds†

In inorganic 5,50-azobistetrazolate (C2N10 2 ; ZT) compounds, the energetic ZT moiety is usually stabilized by H-bonds to lattice H2O and/or coordination of an N-atom of the tetrazole ring to the metal ion. Here we present the synthesis and characterization of a novel, salt-like compound, [Dy(H2O)8]2ZT3, which constitutes a unique exception to the above rule. We used supercritical CO2 as an unconventional desiccant in a straightforward metathesis reaction without abstaining from the benefits aqueous chemistry offers. It caused the crystallization of the title compound with a complex system of H-bonds between [Dy(H2O)8] 3+ and ZT that involves almost every N-atom of the ZT anions as H-bond acceptors, which sufficiently stabilizes the energetic ZT despite the lack of lattice H2O or a coordinative bond to the metal ion.