Ligand scrambling reactions of cyano(thione)gold(I) complexes and determination of their equilibrium constants

Abstract

Ligand scrambling reactions in cyano(thione)gold(I) complexes ([>C=S-Au-CN]) to form [Au(>C=S)2]+ and [Au(CN)2]– species have been investigated for a series of thiones in DMSO using 13C and 15N NMR spectroscopy. Rapid approach to equilibrium occurred and resulted in distinct signals for the [>C=S-Au-CN] and [Au(CN)2]– complexes, both in 13C and 15N NMR. Equilibrium constants (Keq) were determined for scrambling of all the complexes by integrating the CN resonances in the 13C NMR recorded at 298 K. The influence of various factors (initial concentration, ionic strength, temperature, and solvent polarity) on the Keq value was examined for a representative complex (ImtAuCN (Imt = Imidazolidine-2-thione)).Key words: cyanogold(I) complexes, thiones, ligand scrambling, NMR, Keq.

Synthesis and characterization of palladium(II) complexes of thioureas. X-ray structures of [Pd(N,N′-dimethylthiourea)4]Cl2 · 2H2O and [Pd(tetramethylthiourea)4]Cl2

“…The methyl protons of Tmtu also appear as a multiplet instead of singlet after coordination. In 13 C NMR, the [C=S resonance of the ligands in the complexes is shifted upfield by about 4-7 ppm as compared to the free positions in accordance with the data observed for other complexes of silver(I) [3,29,30], gold(I) [31,32], mercury(II) [33], and palladium(II) [34] with thiones. The shift is attributed to the lowering of [C=S bond of N ?…”

Synthesis and Crystal Structures of Cadmium Iodide Complexes of N,N′-Diethylthiourea and 1,3-Diazinane-2-thione

“…The downfield shift is related to an increase in p electron density in the C-N bond upon coordination to Cadmium. In the 13 C NMR spectra of both complexes, the carbon atom of the [C=S unit is shifted upfield by about 1.5 ppm as compared to the free ligand's resonances in accordance with the data observed for other complexes of cadmium(II) [14,26,31,32]. Table 3.…”

“…The selected IR bands of the ligands and their cadmium(II) complexes are given in Table 2. In IR spectra of these complexes, the shifts in the m(C=S), m(N-H) and m(C-N) bands are indicative of coordination of the ligands to the metal center in the solid state [14,26,31,32].…”

Synthesis and Characterization of Antimony(III) Complexes of Thioamides, and Crystal Structure of {[Sb(Imt)2Cl2]2((2‐Imt)}Cl2(Imt=Imidazolidine‐2‐thione)

“…In 13 C NMR as shown in Table 4, only in case of Diaz a significant shift of δ 1.6 was observed compared to free ligand's resonance in accordance with the data observed for other metal-thione compexes. 25,26,29,32,39 For Tmtu complex the shift is δ 0.8, while for the rest of the complexes, the C＝S resonance appears almost unshifted. However, such smaller shifts were also observed for cadmium(II) complexes of thiones.…”

“…In 1 H NMR spectrum of the complexes, the N-H signal of thiones were broadened upon coordination but they were only slightly shifted, although for other complexes of such ligands clear downfield shifts of about δ 0.5-1.0 were observed upon complexation. 25,26,29,32 This may be due to the presence of lone pair on Sb. In 13 C NMR as shown in Table 4, only in case of Diaz a significant shift of δ 1.6 was observed compared to free ligand's resonance in accordance with the data observed for other metal-thione compexes.…”