[Cyclo{tetrakis-mu(3)(eta(2)-S,eta(1)-N)-(1,3-thiazolidine-2-thionato)-bis -(eta(1)-S)-(1,3-thiazolidine-2-thione)tetracopper(I)}]: electrochemical synthesis, characterisation and crystal structure at 160 K

摘要

The complex [Cu-4(tzdt)(4)(tzdtH)(2)] has been electrochemically synthesised in toluene using a copper anode, a platinum cathode and the parent ligand, 1,3-thiazolidine-2-thione (tzdtH). The supporting electrolyte was tetrabutyl ammonium tetrafluoroborate. The major product was the toluene solvated polymer [{Cu-4(tzdt)(4) .(toluene)}(n)] with the title complex obtained as a minor product. The presence of both thionate and thione forms of 1,3-thiazolidine-2-thione was indicated in the title complex by means of IR and proton NMR spectra. The colourless, diamagnetic complex crystallises in an orthorhombic cell with a=21.2452(4), b=24.9586(4), c=11.8536(3) Angstrom, V=6285.4(2) Angstrom(3), Z=8 (tetramers), space group Fdd2, final R1=0.0446 from 1564 reflections with F-0(2)>2 sigma(F-0(2)). The tetranuclear complex has crystallographically imposed C-2 symmetry with the crystallographic axis bisecting the central Cu-4 core of the complex. The central cyclic Cu-4 core of the complex has an 'open-butterfly' configuration with Cu-Cu distances and angles in the range 2.8887(15)-3.8357(16) Angstrom and 47.51(3)-78.27(4)degrees, respectively. The four deprotonated ligands are trinuclear face-bridging, mu(3)-S,N(eta(2)-S,eta(1)-N), towards the four triangular Cu-3 faces of the central Cu-4 core. The 'spinal' copper(I) atoms have distorted trigonal S2N coordination from three different ligands. The 'wing-tip' copper(I) atoms are additionally coordinated by monodentate eta(1)-S donating 1,3-thiazolidine-2-thione ligands and consequently have distorted tetrahedral S3N coordination from four different ligands. Bridging Cu-S distances are in the range 2.225(2)-2.362(2) Angstrom, the monodentate terminal Cu-S distance is 2.4908(18) and the Cu-N distances are 1.996(7) and 2.0017(5) Angstrom. Neighbouring tetranuclear complexes are held together in the solid state by a combination of long-range Cu ... S and S-endo... S-endo contacts. Hydrogen bonds, involving bridging thionate sulfur atoms and the thioamide nitrogen atoms of terminal ligands (NH ... S=3.487 Angstrom), are also involved. The title complex is air-stable and decomposes, endothermically, to copper(II) oxide in flowing air (2.26-836 degrees C). (C) 1998 Elsevier Science S.A. [References: 22]