MACROBICYCLIC D-METAL TRIS-DIOXIMATES OBTAINED BY CROSS-LINKING WITH P-BLOCK ELEMENTS. PART VI. PREPARATION, MOLECULAR STRUCTURE AND MÖSSBAUER (57FE, 119SN) PARAMETERS OF AN IRON(II) COMPLEX WITH A MACROBICYCLIC TIN-CONTAINING TRIS-NIOXIMATE LIGAND

The tin-containing clathrochelate complex of Fe(II) with cyclohexanedione-1,2-dioxime (nioxime, H2Nx), [FeNx3(SnCl3)2]2- · (Et2NH+ 2)2 · Et2NH2 + · Cl− · 2Pri OH was prepared by slowly adding diethylamine to a solution containing the macrobicyclic [FeNx3(SnCl3)2]2- anion. The structure of the complex has been determined by X-ray methods. Crystal data: monoclinic, space group P21/c, a = 10.565(2), b = 25.413(5), c = 20.198(4)Å, β=95.40(3)°, Z = 4. The iron atoms is encapsulated by the clathrochelate ligand and surrounded by a distorted trigonal antiprismatic coordination sphere comprising by six nitrogen atoms of three dioxime residues. The experimental value of the distortion angle (ca 37.5°) is close to that predicted by the Mössbauer (57Fe) parameters (ca 40°). The average Fe-N bond length of 1.923Å is somewhat greater than that in boron-containing analogues. The Sn atoms have a slightly distorted octahedral coordination, which also correspond to Mössbauer (119Sn) spectroscopic data. The six-membered carbocycles in the dioxime fragments have a half-chair conformation with both β-carbons displaced to the opposite sides of the mid-plane of the remaining atoms. All the active hydrogen atoms of the structure are involved in a hydrogen bond system. The possibilities of use of Mössbauer parameters and their temperature dependences to determine the geometry of iron(II) tris-dioximates and the sign of Δ in Mössbauer (57Fe) spectra are discussed.