Synthesis and structure of tetraphenylantimony pentafluoropropionate Ph4SbOC(O)CF2CF3

Tetraphenylantimony pentafluoropropionate has been obtained by the substitution reaction between pentaphenylantimony and pentafluoropropionic acid and by the ligand redistribution reaction between pentaphenylantimony and triphenylantimony bis (pentafluoropropionate) with a yield up to 96 %. The compound has been identified by IR spectroscopy and X-ray diffraction analysis. According to the X-ray diffraction data, the antimony atom has a distorted trigonal-bipyramidal coordination with the oxygen atom of the carboxylate ligand and the carbon atom of the phenyl ligand in apical positions. All fluorine atoms and the carbon atom of the CF3 group are disordered in two positions (the ratio of the contributions of the positions to the disordered fragment is 0.58/0.42). The CSbO axial angle is 178.19(1)º; the sum of the CSbC equatorial angles is 355.78(14)º. The antimony atom is out of the [C3] equatorial plane towards the axial carbon atom at 0.254 Å. The planes of the phenyl rings are rotated around the Sb-Ce bonds so that to minimize intra- and intermolecular interactions. The average Sb-Ce bond length is 2.129(4) Å, while the Sb-Ca bond length is comparable to the equatorial bond length and has the value of 2.124(3) Å. The Sb-O distance is 2.325(3) Å, which is greater than the sum of the covalent radii of antimony and oxygen atoms (2.07 Å). A characteristic feature of all tetraarylantimony carboxylates is the presence of an intramolecular contact between the antimony atom and the carbonyl oxygen atom. This Sb×××O=C distance is 3.492(5) Å, which is less than the sum of the van der Waals radii of antimony and oxygen atoms (3.70 Å). This interaction leads to an increase up to 122.67(14)° in one of the equatorial angles located on the side of the intramolecular contact. The organization of molecules in the crystal is due to hydrogen bonds involving a carbonyl oxygen atom. These contacts structure the molecules into layers that are perpendicular to the crystallographic axis b . Complete tables of atom coordinates, bond lengths and valence angles are deposited at the Cambridge Crystallographic Data Center (No. 1850118; deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif).