{4-Hydroxy-N′-[(2-oxido-1-naphthyl-κO)methylidene]benzohydrazidato-κ2 N′,O}dimethyltin(IV)

Two independent but very similar molecules comprise the asymmetric unit of the title compound, [Sn(CH3)2(C18H12N2O3)]. Each Sn atom is coordinated by two methyl groups and two O atoms and an N atom from the dinegative tridentate ligand. The resultant C2NO2 donor set defines a coordination geometry intermediate between square-pyramidal and trigonal-pyramidal, with a small tendency towards the former. Zigzag chains running along the a axis mediated by O—H⋯N hydrogen bonding characterize the crystal packing. These are connected into layers in the ab plane by a combination of C—H⋯N and π–π [centroid–centroid distances = 3.658 (2) and 3.6740 (18) Å] interactions. The layers are connected along the c axis via C—H⋯O interactions.

Two independent but very similar molecules comprise the asymmetric unit of the title compound, [Sn(CH 3 ) 2 -(C 18 H 12 N 2 O 3 )]. Each Sn atom is coordinated by two methyl groups and two O atoms and an N atom from the dinegative tridentate ligand. The resultant C 2 NO 2 donor set defines a coordination geometry intermediate between square-pyramidal and trigonal-pyramidal, with a small tendency towards the former. Zigzag chains running along the a axis mediated by O-HÁ Á ÁN hydrogen bonding characterize the crystal packing. These are connected into layers in the ab plane by a combination of C-HÁ Á ÁN and -[centroid-centroid distances = 3.658 (2) and 3.6740 (18) Å ] interactions. The layers are connected along the c axis via C-HÁ Á ÁO interactions.

Comment
Interest in the title compound (I) stems from on-going studies into biological and structural aspects of organotin compounds (Affan et al., 2009;Zukerman-Schpector et al., 2009). Two independent molecules comprise the crystallographic asymmetric unit of (I) with the first molecule, Fig. 1, being virtually superimposable upon the second, Fig. 2, there being only small differences in the relative orientations of aromatic rings in the molecules. The similarity between the molecules is reflected in r.m.s. values for bond distances and angles of 0.0063 Å and 1.128 °, respectively. The Sn atom environment in each case is based on a C 2 NO 2 donor set provided by two methyl groups, and the NO 2 atoms of the dinegative, tridentate ligand.
The coordination geometry is intermediate between square pyramidal and trigonal bipyramidal with a leaning towards the former. These assignments are based on the values calculated for τ of 0.48 and 0.43 for the Sn1 and Sn2 atoms, respectively, which compare to the τ values of 0.0 and 1.0 for ideal square pyramidal and trigonal bipyramidal geometries, respectively (Addison et al., 1984).
The crystal packing is dominated by O-H···N hydrogen bonding between the hydroxyl group and the non-coordinating imine-N atoms, Table 1. These lead to the formation of zigzag supramolecular chains along the a axis, Fig. 3.
The molecular structures in (I) resemble closely that found in the dichloromethane solvate (Cui et al., 2007), which also has an intermediate coordination geometry but slightly distorted to trigonal bipyramidal (τ = 0.51). Interestingly, despite the presence of lattice solvent, the supramolecular zigzag chains mediated by O-H···N hydrogen bonding persist in the literature structure.
Experimental 2-Hydroxy-1-naphthaldehyde-4-hydroxybenzhydrazone (0.612 g, 2 mmol) was dissolved in hot absolute methanol (20 ml) in a Schlenk round bottom flask under purified nitrogen atmosphere. Then, a potassium hydroxide solution (0.224 g, 4 mmol) in absolute methanol (5 ml) was added dropwise and the colour of the resulting solution faded from yellow to light-yellow.
The resulting solution was refluxed under a nitrogen atmosphere for 1 h. A solution of dimethyltin(IV) dichloride (0.439 g, 2 mmol) in absolute methanol (5 ml) was added dropwise. The resulting solution was refluxed for 4 h and allowed to cool to room temperature for 30 min. The white precipitate of potassium chloride was removed by filtration. The filtrate was evaporated to dryness using a rotary apparatus under reduced pressure. The yellow crystals obtained were washed with hexane and dried in vacuo over silica gel. Single crystals suitable for X-ray analyses were obtained from the slow evaporation of an ethanol solution at room temperature. Yield: 0.67 g, 53%, and m.pt.540-542 K.
supplementary materials sup-2 Refinement H atoms were geometrically placed (O-H = 0.84 Å and C-H = 0.95-0.98 Å) and refined as riding with U iso (H) = 1.5U eq (O) and U iso (H) = 1.2-1.5U eq (C). Fig. 1. The molecular structure of the first independent molecule of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level.