Syntheses and crystal structures of two magnesium-tetrazole compounds in salt and polymeric forms
Résumé
Two alkaline earth-tetrazole compounds, namely catena-poly[[[triaquamagnesium(II)]―5,5-(azanediyl)ditetrazolato- N-3(1),N-1:N-5] hemi\bis[-5,5-(azanediyl)ditetrazolato-N-3(1),N-1:N-2]bis[triaquama gnesium(II)]\ monohydrate], \[Mg(C2HN9)(H2O)(3)][Mg-2(C2HN9)(2)(H2O)(6)](0.5)H2O\(n), (I), and bis[5-(pyrazin-2-yl)tetrazolate] hexaaquamagnesium(II), (C5H3N6)[Mg(H2O)(6)], (II), have been prepared under hydrothermal conditions. Compound (I) is a mixed dimer-polymer based on magnesium ion centres and can be regarded as the first example of a magnesium-tetrazolate polymer in the crystalline form. The structure shows a complex three-dimensional hydrogen-bonded network that involves magnesium-tetrazolate dimers, solvent water molecules and one-dimensional magnesium-tetrazolate polymeric chains. The intrinsic cohesion in the polymer chains is ensured by NH...N hydrogen bonds, which form R-2(2)(7) rings, thus reinforcing the propagation of the polymer chain along the a axis. The crystal structure of magnesium tetrazole salt (II) reveals a mixed ribbon of hydrogen-bonded rings, of types R-2(2)(7), R-2(2)(9) and R-2(4)(10), running along the c axis, which are linked by R-2(4)(16) rings, generating a 4,8-c flu net.