Synthesis and characterization of sulfonylurea complexes with Cd²⁺, Hg²⁺, and Ag⁺. crystal and molecular structures of K[Cd(chlorpropamide)₃] and Hg(tolbutamide)₂

The synthesis and characterization of Cd²⁺, Ag⁺, and Hg²⁺ complexes with deprotonated tolbutamide and chlorpropanude hgands is described. The crystal and molecular structures of Hg(CH₃C₆H₄SO₂NCONH-n-Bu)₂ (I) and K[Cd(ClC₆H₄SO₂NCONH-n-Pr)₃] (III) are reported. In I the coordination environment around the Hg²⁺ atom is strictly linear and the sulfonylurea ligand is bound in a predominantly monodentate fashion. The tolbutamide ligand is bound through the deprotonated sulfamido nitrogen atom. The Hg-N distance is 2.052 (17) Å. By comparison the chlorpropamide ligand is coordinated to a Cd²⁺ atom in a bidentate mode with both the sulfamido nitrogen and the carbonyl oxygen atoms bound to the metal center. The coordination environment around the Cd²⁺ atom can be best described as trigonal prismatic. The mean Cd-N and Cd-O distances are 2.212 (20) and 2.535 (24) Å, respectively. The counterion K⁺ slightly interacts with the oxygen of the carbonyl and sulfonyl groups in the anion in such a way as to form a polymeric zigzag K⋯Cd chain parallel to the a axis. The IR spectra show (C..^-O) and (C..^-N) stretching frequencies characteristic for either mode of sulfonylurea ligand coordination. On the basis of the IR spectra we propose a structure for K[Ag(p-XC₆H₄SO₂NCONHR)₂] (tolbutamide, X = CH₃ and R = n-Bu; chlorpropamide, X = Cl and R = n-Pr) similar to that of the Hg²⁺ complexes. The ¹H NMR spectra of these compounds are also reported.