Über Tetrazoliumsalze und deren Tetraazaderivate

Abstract

Systematic synthesis of triaryltetrazolium salts, triarylformazans, their Ni-complexes and triarylverdazyls and comparison of our results with literature led to the detection of a characteristic behaviour common to tetraaza compounds of this series which was found to be due mainly to the influence of the C-aryl substituent on these systems. The results are in concordance with findings of Bayer and Häfelinger which confirm our results concerning the homogenisation of bonds in the characteristic segment N=C–N growing from tetrazolium salts to formazan-Ni-complexes. Thus for the C³–N-bonding an increasing hybridization can be derived; varying differences in the bond orders of the single C³=N- and C³–N-bonds make understandable the differing stabilization of cationic forms by electron donating substituents. Considering the system given in formazans stabilized by hydrogen-bridging as “π-deficiency aromatic system” our results show, that “aromatic” character and stability of its cation depend on the degree of hybridization in the segment N=C–N which again depends on the type of C-aryl substitution.