SYNTHESIS, X-RAY CRYSTAL-STRUCTURE AND MAGNETIC STUDIES OF A BISCOPPER(II) COMPLEX OF A C-SPIRO BINUCLEATING LINEAR OCTADENTATE LIGAND

Reaction of the binucleating ligand 5, 5-bis(4-amino-2-thiabutyl)-3, 7-dithianonane-l, 9-diamine (L1) with a copper(II) salt in aqueous solution, and in the presence of lithium dithionate, results in the isolation of a dark blue crystalline solid identified as [Cu2(L1)](S2O6)24H2O. Crystals of the complex are triclinic, space group PI, a 8·227(2), b 13·103(3), c 16·423(4) Å, α 68·68(2), β 86·68(2), γ 75·50(2)°, Z 2, R 0·026 (5039 F). The structure consists of two copper(n) atoms each of which is coordinated through two thioether and two primary amine atoms. The two copper sites are linked through a saturated spiro carbon atom. Each copper atom is also coordinated to one water molecule; one of the copper atoms is coordinated to an oxygen atom of one dithionate anion. Thus, one copper atom is six-coordinate (4+2 tetragonally distorted), and the other is five-coordinate. The intramolecular Cu ·Cu distance is 7·127A; the shortest intermolecular Cu···Cu distance is 6·591 A. The angle between the two N2S2 planes is 92·2°. Low-temperature magnetic studies indicate weak intra- and inter-molecular antiferromagnetic interactions with a singlet-triplet splitting 2J of -10 cm-1 and a 6 of -5 K. E.p.r. studies indicate a magnetic dipole-dipole interaction between the two copper(II) sites and a weak intermolecular antiferromagnetic interaction. © 1990 ASEG.