Within the framework of the conducted systematic research of complexforming ability of SnCl4 in relation to different hydrazone complexes of 2-hydroxybenzoylhydrazones of benz- (2-OH-HBb) and 4-dimethylaminobenzaldehyde (2-OH-HBdb), and also with 2- naphtoylhydrazone of 4-dimethylaminobenzaldehyde (HLdb) of composition [SnCl4(2-OHHBb)]·1,5CH3CN (I), [SnCl4(2-OH-Bdb·H)] (II), [SnCl4(Ldb·H)] (III) are synthesized in acetonitrile. Their single crystals are obtained, a crystalline and molecular structure is certain: in I-III the identical on composition distorted octahedral polyhedron {SnCl4ON} is realized due to four atoms of chlorine and bidentate-cyclic O, N-coordination of ligand (fig. 1-3). Thus in the axial plane of I-III azomethine atom of nitrogen N(1) of ligand and atom of chlorine Cl(2) are situated, and in equatorial plane there are atom of oxygen О(1) of ligand (carbonic in I and оxyazine in II, III) and three atoms of chlorine Cl(1), Cl(3), Cl(4). Introduction of vacant atom of nitrogen (-N(CH3)2) to the aldehyde fragment of molecule of hydrazone causes the change of their coordinated form: ketonic in I and еnolic in II, III). Thus connection of tin with four chloride ions is saved, and a nascent negative charge is compensated due to the protonation of nitrogen atom of dimethylaminogroup. Investigated hydrazones are coordinated to SnCl4 in an identical bidentate-cyclic way. In complex I hydroxygroup does not associate with SnCl4, but engages in intramolecular hydrogen connection with aminogroup О(2)…Н(2)-N(2) (fig. 1). In II intramolecular hydrogen connection is also realized О(2)-Н(2)…N(2), but with participation already of oxyazine atom of nitrogen N(2) and hydrogen of hydroxygroup О(2) – Н(2) (fig. 2). In spite of the fact that II, III have a similar structure, their crystals are not isostructural (monoclinic and threeclinic symmetry correspondingly), they differentiate by the system of hydrogen connections and character of packing of ions. In II ion of Cl(2) forms hydrogen connections N(3)-H(3)Cl(2) with participation of the tertiary ammoniacal atom of nitrogen. In the crystal III, unlike II, two ions of chlorine Cl(1) and Cl(3) participate in formation of hydrogen connection with the tertiary ammoniacal atom of nitrogen N(3): N(3) – Н(3)Cl(1) и N(3) - H(3)Cl(3).figureFig. 1. Structure of IfigureFig. 2. Structure of IIfigureFig. 3. Structure of III