The structure of the amine tautomer of the new Schiff base derived from 4-benzoyl-5-methyl-2-phenyl-2,4-dihydro-pyrazol-3-one (2) and 4-phenyl-thiazol-2-ylamine (3) was confirmed by means of single crystal X-ray diffraction. The title compound (4) was synthesized and crystals were grown from a mixture of dichloromethane and n-hexane (

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Source of materialAs olution of 4-acetyl-2-(3-chloro-phenyl)-5-methyl-2,4-dihydro-pyrazol-3-one (1.0 g, 4mmol) in methanol (30 mL) was added to as olution of 4-p-tolyl-thiazol-2-ylamine (0.76 g, 4 mmol) in methanol (20 mL) under an inert atmosphere. The reaction mixture was refluxed for two hours. Completion of the reaction was monitored by TLC using hexane/ethyl acetate (7:3). The reaction was allowed to cool to room temperature and stirred overnight. Ayellow precipitete formed which wasthen filtered and washed with methanol (10 mL). The crude product, which was purified by crystallization from ethanol, gave yellow crystals. (1.22 g, 72.3% yield, m.p. =462 K). Crystals suitable for xray diffraction were obtained by slow evaporation of the title compound in acombination of dichloromethane with hexane at room temperature. Experimental detailsAll hydrogen atoms, except H3, were placed in idealised positions and refined in riding models with U iso assigned the values to be 1.2 or 1.5 times those of their parent atomsand the constraint distances of C-H ranging from 0.95 Åto0.98 Å. The hydrogen H3 waslocatedinthe electron difference maps and refined freely. .The carbonyl group of pyrazole ring and primary amine of aminothiazolering system are fused to render ac lass of Schiff base ligands. Thediffraction data revealsthatthe nitrogen atom from the2 -aminothiazole moiety (N3) is protonated. The bond between the C3 and C5 carbon atom is adouble bond which indicatest hatthe resulting Schiff base is present as the keto-amine tautomeric forminthe solidstate.There is an intramolecular hydrogen bond between N3 andO12 (H3×××O1 of 1.87(2) Å; see the figure)and the molecules are stacked to create alternating layers across the(110) plane.Z. Kristallogr.