N-(5-Chlorosalicylidene)-2-hydroxy-5-chloroaniline was synthesized and its crystal structure determined. It crystallizes in the orthorhombic space group Pna21 with a = 14.668(4), b = 6.084(3), c = 27.980(4) Å , R = 0.051 for 4788 independent reflections). There are two independent nearly planar molecules in the asymmetric unit. The intramolecular hydrogen bonds occur between the pairs of atoms N1 and O1 [2.553(6) Å], N1 and O2 [2.585(5) Å], N2 and O3 [2.567(6) Å], N2 and O4 [2.620(5) Å], the hydrogen atoms essentially being bonded to the nitrogen atoms. The neighboring molecules are linked via an intermolecular O-H···O hydrogen bond [2.557(5) Å ]. Conformations of the title compound were investigated by semi-empirical quantum mechanical AM1 calculations. The optimized geometry of the molecular structure corresponding to the nearly planar conformation is the most stable conformation in the calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded steric interactions.

The title complex, bis [2-(2-propylirninomethyl) 2435lic derivatives (Pahor, Calligaris, Delise, Dodic, Nardin & Randaccio, 1976); metal complexes of Schiff bases in general have been extensively studied (Calligaris, Nardin & Randaccio, 1972). We describe here the structure of the bis(N-isopropylsalicylideneamino)cobalt(II), (I), complex and compare it with related compounds having different substituents.The two bidentate ligands are coordinated to the Co" ion through their N and O atoms. The geometry around cobalt is somewhat distorted from ideal tetrahedal, mainly as a consequence of the restricted bite of the chelate ligands (reducing intra-ligand O---CO-N angles) and steric repulsion of the isopropyl groups (increasing the N---Co---N angle). The dihedral angle between the two Schiff base ligands, excluding the isopropyl groups, is 82.88 (5) °, so that the two ligands are almost perpendicular, the deviation from an ideal value ) showing the atom-labelling scheme and 50% probability displacement ellipsoids (ORTEPII;.of 90 ° also being due to the isopropyl groups. Geometric differences between the two ligands are minor. The sum of the bond angles at the two N atoms is 360.0 (2) ° in each case, which is appropriate for sp 2 hybridization. The coordination geometry is very similar to that found for corresponding complexes in which the isopropyl groups are replaced by either n-butyl or tert-butyl groups, these complexes retaining the distorted tetrahedral coordination (Bahron, Larkworthy, Marecaux, Povey & Smith, 1994); the mean Co----O and Co-N distances in the present structure are 1.906 (5) and 1.992 (8),~, respectivel)~, with corresponding values of 1.894 (4) and 1.968 (4) A for the averages of the n-butyl and tert-butyl structures. In contrast, linking the two ligands by a two-carbon bridge between the N atoms forces an approximate square-planar coordination geometry in which the Co---O bonds are shorter by about 0.06 and the CoN bonds are drastically shortened by about 0.13 ,~, (Pahor et al., 1976;Hiller, Nishinaga, Tsutsui & Rieker, 1993). Octahedral coordination of Co "I by three similar salicylideneamino ligands gives mean Co----O. and Co--N bond lengths of 1.893 (3) and 1.948 (4)A, respectively, the smaller intrinsic size of the Co I" ion being largely compensated for, as is generally observed, by an increase in the effective size with a larger coordination number (Elerman, Kabak, Svoboda & Geselle, 1994). Experimental Salicylaldehyde (0.2 mmol) and isopropylamine (1 ml) were dissolved in acetonitrile (50 ml). COC12.6H20 (0.1 mmol) in boiling methanol (30 ml) was added and the solution refluxed for 48 h. Suitable crystals were obtained on cooling. ReferencesBahron, H., Larkworthy, L. F., Marecaux, A., Povey, D. C. & Smith, G. W. (1994). J. Chem. Crystallogr. 24, 145-150. Calligaris, M., Nardin, G. & Randaccio, L. (1972). Coord. Chem. Rev. 7, 385--403. Elevman, Y., Kabak, M., Svoboda, I. & Geselle, M. (1994). ActaCryst. C50, 1694-1696. Enraf-Nonius (1993 Ankara, Turkey. E-mail: dulku@...

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Heterodinuclear Complex, Super-Exchange Interactions, Lanthanides Preparation, crystal structure and magnetic properties of a heterodinuclear complex, LCu(Me2C0 )Gd(N03)3 (L = (N,N'-bis(3-methoxysalicylidene)propane-1,2-diamine) are re ported. The crystal structure of the complex was determined by X-ray diffraction methods at 200 K. (Ci9H22N20 4 )Cu(C3H6 0 )Gd(N0 3 )3, monoclinic, space group P2i/c, with a = 9.795(9), b = 18.763(3), c = 15.579(2) A , ß = 95.297(2) V = 2850.9(7) A3 and Z= 4. The central region of the complex is occupied by Cu(II) and Gd(III) ions which are bridged by two phenolato oxygen atoms of the ligand. The copper ion adopts a square-based 4+1 coordination mode, the equatorial N2O2 donors being afforded by the ligand while the axial position is occupied by an oxygen atom of the acetone molecule. The Gd(III) ion is deca-coordinated. In addition to the two phenolate oxygen atoms, the coordination sphere contains two oxygen atoms of the OMe side arms of L and six oxygen atoms from the three bidentate nitrate ions. The G d... Cu separation is 3.425(3) A and the dihedral angle between the GdO(l)Cu and GdO(2)Cu planes is 164.8°. The magnetic susceptibility of the complex was measured over the range 5 -350 K and the observed data were successfully simulated by the equation based on the spin-Hamiltonian operator (H = -/SorSGd), giving the exchange integral 7(Cu-Gd) = 5.6(1) cm-1. This indicates a weak ferromagnetic spin exchange interaction. The nature of the magnetic super-exchange interaction of the title compound is compared with similar [Gd(III)-Cu(II)] heterodinuclear complexes.

599temperature factors (0.020-0.042 A 2) equal to those of their parent atoms. Anisotropic temperature factors assigned to all non-H atoms in final cycles of refinement. Final R--0.068 and wR =0.050 using 2991 'observed' reflections for 289 refined parameters.~w (lFol-IFcl) 2 minimized with w = 1/a2(Fo) where e2(Fo) = cr~ + 0.0000541Fol 2 with a c from counting statistics. (A/tr)max=0-01. A final difference map showed residual fluctuations of-1.7 to 1.6eA -3 (especially close to the I atoms). Scattering factors fromInternational Tables for X-ray Crystallography (1974). SHELX (Sheldrick, 1976) used for structure determination and refinement, PLUTO (Motherwell & Clegg, 1976) for figures.Discussion. Final atom parameters are listed in Table 1, distances and angles in Table 2.* The structure is built up from [Cu(HIO6)2 ]5-, K +, Na + and crystal water. Two distorted IOs(OH) octahedra are joined to a central CuO 4 square by edge sharing (see Fig. 1 ..O(6) bond may be considered, however, as somewhat uncertain from the above discussion. All 26 H atoms are involved in hydrogen bonding. The observed H-atom positions confirm this conclusion although in some cases alternative hydrogen bonds may be proposed. Furthermore, all 12 crystal waters and seven of the 12 oxygen atoms in the anion are coordinated to alkali ions. The four Na ÷ ions are coordinated by six oxygens, and the K ÷ ion is coordinated by seven oxygens. The crystal packing, as viewed down a, is shown in Fig. 2.The stability, shape, hydrogen-bonding capability and charge of the [Cu(HIO6)2] 5-ion make it potentially useful for preparation of heavy-atom derivatives of protein structures. This work has been financially supported by the Swedish Natural Science Research Council (NFR). Acta Cryst. 16, A35. MALAPRADE, L. (1937). C. R. Acad. Sci. 204, 979-980. MALATESTA, L. (1941a). Gazz. Chim. Ital., 71,467-474. MALATESTA, L. (1941b