Structural and NMR studies of the hexameric copper(I) complex with N-n-n-butyl-N′-ethoxycarbonyl-thioureate

The copper sulfide mineral flotation collector, N-n-butyl-N'-ethoxycarbonyl-thiourea (H(2)bectu), and the 1:1 hexameric copper(I) thioureate complex, [Cu(Hbectu)](6), have been characterized by single crystal X-ray diffraction. H(2)bectu crystallizes in the triclinic space group P1 with a = 5.2754(4), b = 9.0042(7), c = 12.6030(9) angstrom, alpha = 80.528(6), beta = 90.173(6), gamma = 76.472(7)degrees. An intramolecular N-H center dot center dot center dot O hydrogen bond between the thioamide proton and carbonyl oxygen forms a planar six-membered ring in the central core of the molecule with C=O, C=S and C-N bond lengths in accord with those reported for other N-alkyl/aryl-N'-acyl-thiourea compounds. [Cu(Hbectu)](6) crystallizes in the monoclinic space group C2/c with a = 23.269(5), b = 13.243(4), c = 23.037(7) angstrom, beta = 91.81(2)degrees as discrete hexameric clusters disposed about a crystallographic centre of symmetry with a Cu(6)S(6) core consisting of two Cu(3)S(3) chair-shaped rings linked by coordination of the deprotonated amide nitrogen atom to a copper atom in the adjacent ring. The six ligands assemble as a paddlewheel structure with the ethoxy and n-butyl substituents packing in an alternating head to tail arrangement. Temperature dependent solution (1)H NMR spectroscopic studies show that the hexameric structure of the complex is maintained in solution.