Coordination compounds with bis(thiosemicarbazonato) ligands represent a class of compounds that can potentially be used as radiopharmaceuticals. It was shown that ethanolic solution of 4-allylthiosemicarbazide reacts with 2,4-pentanedione in 2:1 molar ratio forming 3,5-dimethyl-N-(prop-2-en-1-yl)-5-[2-(prop-2-en-1-ylcarbamothioyl)hydrazinyl]-4,5-dihydro-1H-pyrazole-1-carbothioamide (H2L). Nickel(II) nitrate and perchlorate react with H2L forming the coordination compounds of I and II. In the process of forming these complexes the pyrazolic cycle is breaking up and the compound H2L transforms into 2,2'-(pentane-2,4-diylidene)bis[N-(prop-2-en-1-yl)hydrazinecarbothioamide] (III). In I and II Ni atom adopts a distorted square planar geometry. It coordinates the ligand III via S and N atoms. In the crystal the nitrate and perchlorate ions join the complexes of I and II via hydrogen bonds.