Ab initio molecular orbital method has been used to study the anions of 1-chlorotetrazole (I), 2-chlorotetrazole(II) and 5-chlorotetrazole(III) at the MP2/6-31G level. Fully optimized geometries and electronic structures are obtained. All the title compounds are planar. Their aromaticity and stability are compared. The order of the aromaticity and stability is as follows: (III)>(I)>(II), which predicts the importance and coordination mode of 5-chlorotetrazole as a ligand when forming metallic complexes.

Key words: STABILITY, AB INITIO CALCULATION, TETRAZOLE P, CHLORINE COMPOUNDS, GEOMETRICAL ISOMERISM