Di-μ 2-acetato-1:2κ 2 O:O′;2:3κ 2 O:O′-bis{μ 2-4,4′-dichloro-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethanylylidene)]diphenolato}-1:2κ 6 O,N,N′,O′:O,O′;2:3κ 6 O,O′:O,N,N′,O′-tricadmium

In the title linear homo-trinuclear complex, [Cd3(C19H18Cl2N2O2)2(C2H3O2)2], the central CdII atom is located on a centre of inversion and has a distorted octahedral coordination geometry formed by four O atoms from two bidentate/tetradentate Schiff base ligands and two O atoms from two bridging acetate ligands. The coordination geometry of the terminal CdII atom is square-pyramidal with the tetradentate part of the ligand in the basal plane and one O atom from an acetate ligand occupying the apical site. The six-membered CdN2C3 ring adopts a chair conformation. The acetate-bridged Cd⋯Cd distance is 3.3071 (2) Å. The crystal structure is stabilized by C—H⋯O hydrogen bonds, which form C(7) chain motifs and give rise to a two-dimensional supramolecular network structure lying parallel to the ab plane.

In the title linear homo-trinuclear complex, [Cd 3 (C 19 H 18 Cl 2 -N 2 O 2 ) 2 (C 2 H 3 O 2 ) 2 ], the central Cd II atom is located on a centre of inversion and has a distorted octahedral coordination geometry formed by four O atoms from two bidentate/ tetradentate Schiff base ligands and two O atoms from two bridging acetate ligands. The coordination geometry of the terminal Cd II atom is square-pyramidal with the tetradentate part of the ligand in the basal plane and one O atom from an acetate ligand occupying the apical site. The six-membered CdN 2 C 3 ring adopts a chair conformation. The acetatebridged CdÁ Á ÁCd distance is 3.3071 (2) Å . The crystal structure is stabilized by C-HÁ Á ÁO hydrogen bonds, which form C(7) chain motifs and give rise to a two-dimensional supramolecular network structure lying parallel to the ab plane.

Comment
Metalloligands are metal-complex molecules which can act as ligands by reacting with other metal ions to form, for example, polynuclear complexes, coordination polymers and metal-organic frameworks. Recently metalloligands have received much attention, because of their functional properties and many potential applications, such as luminescence, catalysis, magnetism, gas storage, ion recognition, see: Du et al. (2012), Carlucci et al. (2011) and Das et al. (2011). The metal complexes with Schiff base ligand, bis(salicylidene)propane-1,3-diamine can be metalloligands, forming linear homo-or hetero-triuclear complexes with divalent metal salts, see: , Das et al. (2013) and Fukuhara et al. (1990). We have recently studied the structure of a homo-trinuclear Cu II complex with tetradentate bischlorosalicylidene, 4,4′-dichloro-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethanylylidene)]diphenol and copper acetate units as the building blocks. (Kubono et al., 2012). It can be considered that the compound is a 1:2 metal-complex between a copper(II) ion and a Cu II mononuclear complex, which acts as a metalloligand. Subsequently, we have tried to synthesize further trinuclear complexes with the same ligand and other metal ions. Herein, the structure of the title cadmium-based trinuclear complex, containing the tetradentate Schiff base ligand and cadmium acetate units, is reported.
The central Cd II atom, Cd2, is located on a centre of inversion and has a distorted octahedral coordination enviroment, formed by four oxygen atoms from two tetradentate Schiff base ligands in the equatorial plane and an oxygen atom from each of the two bridging acetate ligands in the axial positions. The terminal Cd II atom, Cd1, has a distorted squarepyramidal configuration with atoms in the basal plane comprising two phenolate O and two imine N atoms from the tetradentate ligand. The apical site is occupied by one O atom from an acetate bridging ligand. Cd1 is located at 0.77466 (10) Å above the mean basal plane (N1/N2/O1/O2) of the square-based pyramid. The six-membered Cd1/N1/C8/C9/C10/N2 ring adopts a chair conformation with puckering parameters (Cremer & Pople, 1975): Q = 0.6280 (15) Å, θ = 3.29 (14)° and φ = 251 (2)°. The bond lengths and angles involving Cd II atoms are comparable to those observed in related linear homo-trinuclear Cd II complexes (Atakol, Aksu et al., 1999;Xue et al., 2012). The dihedral angle between the benzene rings (C1-C6 and C14-C19) is 71.88 (7)°, a value comparable with that found in the related trinuclear Cu II complex (Kubono et al., 2012). The Cd1···Cd2 distance is 3.3071 (2) Å, similar to that found in related structures (Atakol, Aksu et al., 1999;Xue et al., 2012). In the crystal structure of the title complex, there is an intermolecular C15-H15···O3 i hydrogen bond [symmetry code: (i) -x + 1/2, y + 1/2, z; Table 1], forming a C(7) chain motif (Bernstein et al., 1995). C15-H in the benzene ring at (x, y, z) acts as hydrogen bond donor to atom O3 from an acetate at (-x + 1/2, y + 1/2, z), so forming a C(7) chain running parallel to the b-axis and generated by the b-glide plane at x = 1/4. The crystal structure is stabilised by intermolecular C-H···O hydrogen bonds, which form a two-dimensional supramolecular network structure parallel to the ab plane with an R 4 4 (34) graph-set ring motif (Fig. 2).

Refinement
All H atoms bound to carbon were placed at idealized positions and refined using a riding model, with C-H = 0.95-0.99 Å and U iso (H) = 1.2U eq (C).

Figure 1
The title compound with displacement ellipsoids drawn at the 50% probability level.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).