X-ray structural analysis of the dinitratotetrapyridinecopper(II) complex and its clathrates with tetrahydrofuran and chloroform

The structure of the [CuPy4(NO3)(2)] complex (Py = pyridine) and its clathr ates with tetrahydrofuran and chloroform (both with a host:guest molar rati o of 1:2) were determined by the single-crystal XRD method (CAD-4 diffracto meter; CuKalpha radiation, graphite monochromator). The three structures ar e molecular, with van der Waals intermolecular contacts. The main structura l parameters of the [CuPy4(NO3)(2)] molecule air preserved in the clathrate s. The coordination of copper(II) consisting of four nitrogen atoms of the pyridine ligands and two oxygen atoms of the monodentate nitrate groups in the trans-position is severely distorted due to the lengthened Cu-O bonds ( 2.46-2.61 Angstrom). In the complex phase, the pyridine lines of the molecu le are nearly perpendicular to the equatorial plane, whereas in the clathra tes the molecule has a propeller conformation. The clathrates are isomorpho us with each other and with other compounds of the general formula [MPy4X2] . 2G. Close relationship between the structural types of the [MPy4X2]. 2G c lathrates is revealed. The anomalous stability of [CuPy4(NO3)(2)] compared to the analogous Mn, Co, Ni, Zn, and Cd complexes, which can only exist in clathrate form, is explained.