Crystal and Solution Structures of N,N-Dimethylthioformamide-Solvated Copper(I), Silver(I), and Gold(I) Ions Studied by X-ray Diffraction, X-ray Absorption, and Vibrational Spectroscopy

Crystal structures of the solvated copper(I) and silver(I) perchlorate salts crystallizing from N,N-dimethylthioformamide solution have been determined by single-crystal X-ray diffraction at 295 K. Tetrakis(N,N-dimethylthioformamide)copper(I) perchlorate, [Cu(SCHN(CH₃)₂)₄]ClO₄, crystallizes in the monoclinic space group P2/n (No. 13) with a = 8.428(2), b = 9.605(2), and c = 15.096(3) Å, β = 104.35(2)°, and Z = 2. The copper(I) ion in a site of C₂ symmetry coordinates four N,N-dimethylthioformamide ligands in a slightly distorted tetrahedral coordination with Cu−S bond distances of 2.3249(8) and 2.3494(8) Å. The triclinic (P1̄, No. 2) tris(N,N-dimethylthioformamide)silver(I) perchlorate, Ag(SCHN(CH₃)₂)₃ClO₄, with a = 7.4149(5), b = 7.7953(5), and c = 17.1482(1) Å, α = 98.341(5), β = 93.910(5), and γ = 107.084(5)°, and Z = 2, contains centrosymmetric Ag₂(SCHN(CH₃)₂)₆²⁺ dimers in which two almost planar AgS₃ units are held together by an asymmetric double sulfur bridge with one short and one long Ag−S bond, 2.529(1) and 2.930(1) Å, respectively. The Ag−S bond distances to the two terminal N,N-dimethylthioformamide ligands are 2.469(1) and 2.543(1) Å. The solvated copper(I) and silver(I) ions in solution were found by means of large-angle X-ray scattering (LAXS) to coordinate four N,N-dimethylthioformamide molecules with the mean Cu−S and Ag−S bond distances 2.36(1) and 2.58(1) Å, respectively, probably with distorted tetrahedral coordination geometry, while an EXAFS study gave the Cu−S bond distance 2.34(1) Å. EXAFS studies showed a linear S−Au−S entity with an Au−S bond distance of 2.290(5) Å in the structure of the solid bis(N,N-dimethylthioformamide)gold(I) tetrafluoroborate, Au(SCHN(CH₃)₂)₂BF₄. The structure in solution is similar with a mean Au−S bond distance of 2.283(4) Å. Raman and infrared vibrational spectra of the solvated copper(I), silver(I), and gold(I) ions in the solid state and N,N-dimethylthioformamide solution have been recorded and assigned.