Synthesis, structure and thermal behaviour of two magnesium complexes containing the 1,4-bis(5-tetrazolyl)benzene ligand

The reaction between the 1,4-bis(5-tetrazolyl)benzene ligand (H2btb) and different Mg salts allowed the recovery of two different mol. salts, [Mg(H2O)6](btb) (1) and [Mg(H2O)6](Hbtb)22H2O (2). These cryst. materials were fully characterized by spectroscopic, thermal and diffraction methods. In both cases the octahedrally coordinated hexaaquo Mg(II) ions are linked through several strong H-bond interactions of the OHN type to the btb anions, completely or partially deprotonated in 1 and 2, resp. The thermal anal. established that, in both cases, all H2O mols. are lost <200. The process is completely reversible upon exposure to H2O-satd. atm. Unfortunately, the anhyd. phases are amorphous, and no structural information could be derived form the authors' PD traces, even if a no. of partially cryst. intermediates, formed during the dehydration processes, were obsd. by thermodiffractometric methods.