The reversible formation of tight ion pairs within platinum(II) complexes - A study of thermodynamic parameters governing noncovalent interactions

Compounds like [(HR2DTO)Pt(H2R2DTO)][Cl] (DTO =dithiooxamidate; R = ethyl or benzyl) can be involved in acid-base reactions in chloroform, playing the role of either the acid or the base partner. When the complexes react with pyridines, neutral complexes like [(HR2DTO)2Pt] are formed. Such processes are characterized by small enthalpy changes, so they are substantially entropy-driven. We explained this as a consequence of the solvent released when HCl is transferred from tight-ion-pair platinum compounds to pyridines. When [(HR2DTO)Pt(H2R2DTO)][Cl] species react with HCl, complexes like [(H2R2DTO)Pt(H2R2DTO)][Cl]2 are formed, where a new weak hydrogen-bonding-based interaction of the type N···H-Cl