Structural Studies of Organic Silver Complexes in Dimethyl Sulfoxide by ¹³C and ¹⁰⁹Ag NMR

The effects on, ³C and ¹⁰⁹Ag chemical shifts of complexation of ethylenethiourea, thiazolidine-2-thione, 3-methylthiazolidine-2-thione, dipropylamine, pentamethylene sulfide, and 2-aminothiazole with silver nitrate in dimethyl sulfoxide solution have been examined. Although complexation is reflected via ¹⁰⁹Ag chemical shifts of hundreds of parts per million, as compared with only a few parts per million of ligand ¹³C chemical shifts, both types of NMR data suggest that ligands which bind Ag(I) through sulfur form solutions containing a variety of complex species. By contrast, nitrogen ligands appear to form primarily 2:1 silver-to-ligand complexes. The ¹³C chemical-shift changes in the unsaturated compounds are discussed in terms of contributions from resonance forms containing different degrees of C=S and C=N bonding in the silver complexes compared to the free ligands.