Tetrapyridineplatinum(II) Carboxylates: Synthesis and Crystal Structure

A series of mono- and bimetallic cation-anionic complexes based on the [PtPy₄]²⁺ cation with different single-charge anions of carboxylic acids (RCOO^–) is synthesized and structurally characterized. A synthetic approach to the preparation of tetrapyridineplatinum complexes [PtPy₄]²⁺ soluble in polar solvents from available reagents is developed. The reaction of tetrapyridineplatinum dichloride [PtPy₄](Cl)₂ with silver acetate or trifluoroacetate affords compounds [PtPy₄](OOCMe)₂·6H₂O (I) and [PtPy₄](OOCCF₃)₂· 2H₂O (II) in the form of crystalline hydrates (CIF files CCDC nos. 2161100 and 2161101, respectively) in high yields. Other carboxylates can be prepared by the treatment of compound I with an excess of a stronger acid, for example, trifluoroacetic acid, with the formation of the corresponding complex trifluoroacetate [PtPy₄](OOCCF₃)₂·4CF₃COOH (IIa) (CIF file CCDC no. 2161102). Another method consists of the displacement of acetic acid with an excess of a lowly volatile acid, for example, pivalic acid, when [PtPy₄](Piv)₂· 5HPiv (III) is formed from the acid melt, and solvatomorph [PtPy₄](Piv)₂·4HPiv·3C₆H₁₂ (IIIa) (CIF files CCDC nos. 2161103 and 2161104, respectively) is formed in a cyclohexane medium. Heteroanionic heterometallic complex [PtPy₄](OOCFc)(OOCMe) (IV) (CIF file CCDC no. 2161105) is shown to be formed by the reaction of complex I with ferrocenecarboxylic acid under mild conditions.