The structure of 1-phenyl-3-methyl-4-benzoylpyrazol-2-in-5-selenone and its derivatives

It is shown that 1-phenyl-3-methyl-4-benzoylpyrazol-2-in-5-selenone exists in a SeH-tautomeric form in the solid phase. Crystal and molecular structure of bis(1-phenyl-3-methyl-4-benzoylpyrazolyl-5)selenide as a supplementary product of the synthesis of selenopyrazolone and di(1-phenyl-3-methyl-4-benzoylselenopyrazolyl-5)diselenide as the product of oxidation of the latter were characterised by X-ray single crystal diffraction.