Interaction of hexachloroplatinum hydrocacid with 2,2'-bipyridine and 1,2,3,4-tetrahydroacridine-9-carboxylic acid: structure of reaction products

The product of the reaction of hexachloroplatinic acid with 2,2'-bipyridine in a water-acetonitrile mixture at room temperature is 2,2'-bipyridinium hexachloroplatinate(IV) [C10N2H8∙H]+2[PtCl6]2- (I). Under the same conditions, hexachloroplatinic acid protonates 1,2,3,4-tetrahydroacridine-9-carboxylic aсid at the nitrogen atom to form the dihydrate [C28N2О4H30∙H]+2[PtCl6]2-×2Н2О (II). New complexes with hexachloroplatinate anions were characterized by X-ray diffraction analysis at 293(2) K (Bruker D8 Quest, MoKα radiation, λ = 0.71073 Å, graphite monochromator). Centrosymmetric [PtCl6]2- anions in complexes I and II have similar geometric characteristics (the Pt-Cl bonds are 2.3211(9)-2.3340(8) Å, the ClPtCl angles are 89.71(3)°-90.31(3)°). Cation I is 2,2'-bipyridine molecule protonated at one of the nitrogen atoms with a weak intramolecular hydrogen bond N-H×××N (2.20 Å). In complex II, the cation is 1,2,3,4-tetrahydroacridine-9-carboxylic acid protonated at the nitrogen atom of the heterocycle. The short contacts observed in crystal I are caused by weak intermolecular bonds of the N-H×××Cl (2.69 Å) and C-H×××Cl (2.85-2.94 Å) types, with each anion surrounded by eight cations and each cation surrounded by four anions. In crystal II chain-like structural units can be distinguished. In these chains the anion forms hydrogen bonds О-Н×××Cl (2.34 Å) through the carboxyl groups with two cations, which are bound to water molecules through the protonated nitrogen atom N-H×××O (1.91 Å). The chains are connected to each other by weaker interactions, among which are the hydrogen bonds О-Н×××Cl (2.54 and 2.77 Å) between water molecules and anions.