Crystal Structure of [Cu4(tu)](SO4)2·H2O and Vibrational Spectroscopic Studies of Some Copper(I) Thiourea Complexes

Abstract

The complex [Cu4(tu)7](SO4)2·H 2O was isolated by addition of thiourea to a copper(II) sulfate electrolyte solution consisting of 2 M H2SO4 and 0.7 M CuSO4. The crystal structure of this complex was solved by X-ray methods and highlighted a [Cu4(tu)7]4+ adamantane cluster. A copper(I)-thiourea cluster of this stoichiometry has not been previously reported. The X-ray structure is refined to residual R = 0.0447 for 4093 observed reflections. Crystals are orthorhombic, of space group Pbca, with Z = 8 in a cell of dimensions a = 10.414(3), b = 17.909-(3), and c = 35.818(3) Å. The copper atoms lie in a tetrahedral arrangement in which one of the copper atoms is four-coordinate, while the other three display trigonal planar coordination with Cu⋯Cu distances of 2.899-(2)-2.967(2)Å. The copper-thiourea clusters are interlinked by sulfate ions, which strongly interact with the thiourea ligands through hydrogen bonds. The infrared and Raman spectra of the title compound and of the related copper(I) thiourea complexes [Cu2(tu)5](SO4)·3H2O, [Cu2(tu)6](SO4)·H2O, [Cu4(tu)6](NO3)4·4H 2O, and [Cu4(tu)9](NO3)4·H 2O were recorded and assigned, and the dependence of ν(CuS) on the coordination environment of the copper was established.