Tri- and Tetraphenylantimony 3,3,3-Trifluoropropanates: Synthesis and Structure

Abstract

Triphenylantimony bis(3,3,3-trifluoropropanate) (I) to be converted into tetraphenylantimony 3,3,3-trifluoropropanate (II) after additional treatment with pentaphenylantimony has been synthesized by the reaction between triphenylantimony and 3,3,3-trifluoropropanoic acid (HL) in the presence of tert-butyl hydroperoxide. The hydrolysis of complex I leads to the formation of µ₂-oxo-bis(3,3,3-trifluoropropanatotriphenylantimony) (III). Complex II has also been synthesized from HL and pentaphenylantimony. The solvate Ph₄SbOC(O)CH₂CF₃ ⋅ HOC(O)CH₂CF₃ (IV) has been isolated from the reaction mixture at an acid excess (2 : 1 mol/mol). According to X-ray diffraction data, the Sb atoms in complexes II–IV have differently distorted trigonal bipyramidal coordination. The СSbO axial angles in complexes II and IV are 173.29(7)° and 178.06(11)°, respectively. In a centrosymmetric molecule of complex III (the inversion center is the bridging oxygen atom), the OSbO angles are 175.64(6)°. The Sb–O and Sb–С bond lengths are 2.255(2) and 2.109(2)–2.167(2) Å in II; 1.8169(3), 2.045(2) and 2.065(2)–2.403(3) Å in III; 2.319(3) and 2.110(4)–2.168(3) Å in IV. The Sb⋅⋅⋅O intramolecular distances with the carbonyl oxygen atom (3.414(3) Å (II), 3.232(4) Å (III), 3.233(4) Å (IV)) are ~0.3–0.5 Å smaller than the sum of the antimony and oxygen van der Waals radii.