Adducts of bis-(2-Guanidinium Benzimidazole) Copper II Salts with Ammonia and Pyridine

The four coordinated bis-(2-Guanidinium Benzimidazole) Copper II complexes change to hexa coordination when treated with ammonia gas. The resulting adducts have high magnetic moments (2·09 B.M.). In presence of pyridine the four coordinated copper complexes, however, could be converted to both penta and hexa coordinated adducts. The magnetic moments of pyridine adducts lie between 1·84-1·99 B.M. The electronic absorption spectra in pyridine show two wide peaks at 13·4 and 18·0 kk region. which support the octahedral structure. From the ratio  σ Cu/σ Ni = 1·28 the structure is found to be moderately tetragonal.