Synthesis and structure of inclusion complex of tetraphenylphosphonium benzoate with benzoic acid

Special interest in studying the structure of adducts of tetraphenylphosphonium carboxylates is due to the fact that they have not been previously described in the literature. For the first time we have described the data, based on X-ray diffraction analysis, for synthesis and structure of the inclusion complex of tetraphenylphosphonium benzoate with benzoic acid (1). Inclusion complex 1 has been obtained by interaction of pentaphenylphosphorus with benzoic acid at the mole ratio of 1:2 in benzene. Pale yellow crystals with a clear melting point are highly soluble in aromatic hydrocarbons and polar solvents. In the IR spectrum of adduct 1, vibrations of the P-Ph groups are observed as an intense band with an absorption frequency of 1438 cm-1. Bands of average intensity at 995 and 1024 cm-1 can be related to the deformation vibrations of the P-Ph groups. According to the X-ray diffraction data, in crystal 1 there are two types of crystallographically independent ion pairs and solvate molecules of benzoic acid. Tetraphenylphosphonium cations have a slightly distorted tetrahedral configuration. The СРС valence angles are 106.28(16)-112.56(17)° (1 а ), 106.15(16)-112.03(17)° (1 b ). The Р-С distances are 1.782(3)-1.800(4) Å (1 а ), 1.784(4)-1.794(3) Å (1 b ). The С-О bond lengths in the carboxylate anions are: С(107)-О(5) 1.250(5) Å and С(107)-О(6) 1.227(5) Å (1 а ), С(87)-О(1) 1.297(5) Å and С(87)-О(2) 1.216(4) Å (1 b ). The О(6)С(107)О(5) (1 а ) and О(2)С(87)О(1) (1 b ) valence angles in the anions are 125.9(4)° and 123.6(4)°, respectively. It should be noted that the solvate molecules of benzoic acid are located in the cavities between tetraphenylphosphonium cations. In this case, their carboxyl groups are directed to the COO- groups of carboxylate anions. Complete tables of coordinates of atoms, bond lengths and valence angles are deposited at the Cambridge Structural Data (№ 1983589; deposit@ccdc.cam.ac.uk или http://www.ccdc.cam.ac.uk/data_request/cif).