Competing coordination at donor atoms in 1,3,4-thiadiazole derivatives

Energy parameters of 1,3,4-thiadiazole derivatives were calculated by the M NDO semiempirical method, and the calculation results were used to interpre t competing coordination at the donor nitrogen atoms with regard to the sub stituent in the heteroring. Prediction of the coordination sites in 2-amino -1,3,4-thiadiazole and 2-amino-5-ethyl-1,3,4-thiadiazole was consistent wit h the X-ray diffraction data for Zn(II) complexes with these ligands.