Synthesis and Structure of Tris(2-methoxyphenyl)antimony Bis(2,5-difluorobenzoate)

Abstract

Tris(2-methoxyphenyl)antimony bis(2,5-difluorobenzoate) (1) has been obtained by the oxidative addition reaction between tris(2-methoxyphenyl)antimony, 2,5-difluorocarboxylic acid and tertiary butyl hydroperoxide in diethyl ether with the 72% yield. The compound has been identified by IR spectroscopy and X-ray diffraction analysis. According to the X-ray diffraction data, the crystal of compound 1 contains two types of crystallographically independent molecules a and b, the geometric parameters of which are slightly different. In molecules a and b the antimony atoms have a distorted trigonal-bipyramidal coordination with the oxygen atoms of the carboxylate ligands in the axial positions. The crystal also contains a solvate molecule of diethyl ether, disordered in two positions. The updated ratios of position contributions are 0.50/0.50. The sums of the CSbC angles in the equatorial plane of molecules 1a and 1b are 359.9(3)° and 359.8(3)°, respectively. The OSbO axial angles are 174.60(16)° (1a) and 175.51(17)° (1b). The antimony atom departs from the equatorial plane [C3] by 0.040 Å for both molecules. The conformation of the aryl ligands with respect to the equatorial plane [C3] is propeller-like. The SbC bond lengths have close values: 2.097(7)2.127(6) Å in 1a, 2.107(7)2.115(6) Å in 1b. The SbO distances (2.112(5), 2.131(5) Å in 1a, 2.107(5), 2.128(5) Å in 1b) are commensurate with the covalent SbO bond lengths. Bidentate carboxylate ligands are coordinated to the metal atom less symmetrically in molecule 1а, while the SbO(=С) intramolecular distances are 3.116(7), 3.063(7) Å in 1a, and 3.120(6) Å, 3.126(7) Å in 1b, which is less than the sum of the van der Waals radii of the Sb and O atoms. In molecules 1a and 1b short distances are observed between the oxygen atoms of the methoxy groups and the antimony atoms (3.080(6), 3.138(7), 3.164(4) Å for 1a, 3.023(6), 3.085(5), 3.194(7) Å for 1b), which increases the coordination number of the antimony atom. The structure of the crystal is presented in such a way that the solvate molecules of diethyl ether, arranged in one chain of the form (∙∙∙СH3CH2OCH2CH3∙∙∙F∙∙∙)n, are surrounded by molecules of tris(2-methoxyphenyl)antimony bis(2,5-difluorobenzoate), forming a shell of sorts for a chain of ether molecules. This interaction is due to hydrogen bonds: –ОСH(СH3)–H∙∙∙F, Et2O∙∙∙HMeO–, –ОСH2CH2–H∙∙∙F. Molecules of the a and b types contact each other through hydrogen bonds С=О∙∙∙HMeO–, F∙∙∙HMeO–, F∙∙∙HAr, and Sb–O∙∙∙HAr. Also, the СН∙∙∙π interactions and the stacking effect are observed in the packing of molecules. Complete tables of atom coordinates, bond lengths and valence angles are deposited at the Cambridge Crystallographic Data Center (No. 2077192 (1), deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif).