Structural and spectroscopic studies of some adducts of silver(i) halides with thiourea and N-ethyl substituted thioureas

Abstract

Syntheses, single crystal X-ray structural and spectroscopic characterizations are described for a variety of adducts of silver halides with thiourea (‘tu’), N-ethylthiourea (‘ettu’ = EtNH·CS·NH₂) and N,N′-diethylthiourea (‘detu’ = EtNH·CS·EtNH). This study greatly extends our knowledge of the complex chemistry of silver(I) halides with tu. The unexpected diversity of composition of such complexes was initially revealed by the powerful mechanochemical/IR method and the structures of several of the new complexes were determined by X-ray crystallographic studies of samples subsequently prepared from aqueous solution. Structural characterizations provide extensive geometrical data for (mononuclear 1 : 3) [XAg(xtu)₃] arrays (xtu = ettu, detu; X = Cl, Br, I), assisting vibrational spectroscopic assignments. With the parent tu ligand, binuclear ionic forms are obtained: [tu₂Ag(μ-tu)₂Agtu₂]X₂, the chloride as the dihydrate and the bromide as a di(thiourea) dihydrate adduct. With tu 1 : 2 complexes are defined for X = Cl, Br, as isomorphous one-dimensional polymers; AgCl:tu (1 : 1) is a two-dimensional net with six-membered Ag₃S₃ rings and terminal chloride. Intermediate stoichiometries are defined in AgBr:tu (2 : 3), a one-dimensional polymer of Ag₂S₂ rhombs linked at the silver atoms, while [Cl₂Ag₃(tu)₄](NO₃)·H₂O is also a one-dimensional polymer in which chloride and thiourea sulfur atoms link six-membered Ag₃S₃ rings. Diagnostic bands in the IR and far-IR spectra of all of the synthesized complexes are assigned and interpreted in relation to the structures.