Polymeric palladium(II) dicarboxylate complexes with НOOC–R–COOH, where R is CH=C(CH3), CH2–C(=CH2), or CH=CH: Unconventional transformation of palladium citraconate with the formation of a metal chelate with the Pd–C bond in the tetranuclear complex [Pd(μ-OОC)С(СН3)(OH)СН(COOH)(CH3CN)]4 ∙ 2H2O

Abstract

Polymeric palladium complexes with citraconic, itaconic, and maleic acids [Pd(μ-OOC–R–COO)(H₂O)]n · (0.1 НOOC–R–COOH)_n, where R is CH=C(CH₃) (1), CH₂–C(=CH₂) (2), or CH=CH (3), in which the coordination surrounding of palladium consists of bridging acid carboxylate groups and complemented with water molecules linked by hydrogen bonds to the oxygen atoms of the non-coordinated carboxylate groups of citraconic, itaconic, and maleic ions, have been synthesized for the first time. The reaction between palladium citraconate 1 and CH₃CN in acetone results in the tetranuclear complex [Pd(μ- OОC)С(СН₃)(OH)СН(COOH)(CH₃CN)]₄ · 2H₂O (4), whose structure has been characterized by X-ray diffraction. The reduction of the double bond in the citraconate ion and, as a consequence, the formation of the Pd–C bond result in that each of the four palladium atoms forms a five-membered chelate ring linked to the second non-coordinated carboxylate branch of citraconic acid.