Di-μ-azido-bis(μ-1,4,7,10,13,16-hexaoxacyclooctadecane)bis(5,10,15,20-tetraphenylporphyrinato)dicadmiumdisodium

The asymmetric unit of the title compound, [Cd2Na2(N3)2(C44H28N4)2(C12H24O6)2], consists of one half of the dimeric complex; the tetranuclear molecule lies about an inversion centre. The CdII atom is coordinated by the four pyrrole N atoms of the 5,10,15,20-tetraphenylporphyrinate ligand and one N atom of the axial azide ligand in a square-pyramidal geometry. The azide group is also linked to the NaI atom, which is surrounded by one 18-crown-6 molecule and additionally bonded to a second 18-crown-6 molecule trans to the azide group. The porphyrin core exhibits a major doming distortion (∼40%) and the crystal structure is stabilized by weak C—H⋯π interactions. The molecular structure features weak intramolecular hydrogen bonds: two O—H⋯O interactions within the 18-crown-6 molecule and one C—H(18-crown-6)⋯N(azido) contact.

We report herein on the molecular structure of the title compound. The Cd atom is five-coordinated bound to the four porphyrin N atoms and to the nitrogen N5 atom of the azido ligand (Fig. 1) The most interesting features of the structure of (I) are: (i) each [Cd(TPP)(N 3 )]complex ion is strongly linked to the sodium atom of the counterion [Na(18-crown-6)] + through the nitrogen N7 of the azido ligand where the Na __ N(azido) distance is 2.492 (2) Å, (ii) the sodium atoms of two symmetry related [Na(18-C-6)] + counterions are linked by two strong Na-O distances where the Na + belongs to one 18-crown-6 molecule and the oxygen atom belong to the symmetry related adjacent ether crown molecule. The value of this distance [2.540 (1) Å] is shorter than the average Na-O(18crown-6) which is 2.703 (2) Å.
The molecular structure of (I) shows the presence of weak intramoleculair hydrogen bonds: two O-H···O bonds within the 18-crown-6 molecule and one C-H(18-crown-6)···N6(azido) bond. The crystal packing of the title compound is stabilized by C-H······π intermolecular interactions involving Cg pyrrole and phenyl centroids rings (Table 1 and Fig. 2).

Experimental
The [Cd(TPP)] complex (Rodesiler et al. 1985) (20 mg, 0.027 mmol) with an excess of sodium azide NaN 3 (100 mg, 1.5 mmol) and 18-crown-6 (52 mg, 0.19 mmol) in chlorobenzene (10 ml) were stirred overnight at room temperature under air to yield a dark-purple solution. Crystals of the title complex were obtained by diffusion of hexanes through the chlorobenzene solution.

Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.99 Å (methylene) and 0.95 Å (aromatic) with U iso (H) = 1.2U eq (C aromatic, methylene ).
Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > σ(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. Rfactors based on F^2^ are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.