Synthesis and Structure of Dioxomolibdenum(VI) Complexes with Hydrazones of β-Dicarbonyl Compounds. Crystal Structures of Benzoylacetone Nicotinoylhydrazone (H2L¹), Acetoacetanilide Benzoylhydrazone (H2L²), and MoO2L¹·MeOH Solvate

Two acetylhydrazones, namely benzoylacetone nicotinoylhydrazone (H2L1) and acetoacetanilide benzoylhydrazone (H2L2), and also the MoO2L1·MeOH solvate complex were synthesized and their structure was studied by single crystal X-ray diffraction and IR-spectroscopy methods. Molecules of two hydrazones crystallize in different enehydrazonic tautomeric forms: hydrazonic for H2L1 and enehydrazine-α-oxyazine for H2L2. In the both organic molecules, two planar six-membered aromatic cycles are connected by zigzag six- and seven-membered C–C–C–N–N(H)­–C– and –N–C–C–C–C–N–N–C– chains, respectively. The both organic molecules are stabilized by N–H···O intermolecular hydrogen bonds (and also by N–H···O intramolecular hydrogen bond in the H2L2 structure). In the MoO2L1·MeOH solvate, the molybdenum atom has an octahedral coordination environment formed by two cis-O2(oxo) and tridentate (ONO)bis(chelate) (L2)2– ligands, and also a methanol molecule. Atoms N(L1) and O(MeOH) are in trans-position to O(oxo); two atoms O(L1)—in cis-position to O(oxo) and trans-position to each other.