Synthesis and Structure of Tris(dicarboxylates) (m-tolyl)antimony

Abstract

By an oxidative addition reaction the previously unknown tris(m-tolyl)antimony dicarboxylates were obtained: m-Tol₃Sb[OC(O)C₆HF₄]₂ (1) with a yield of 80 % and m‑Tol₃Sb[OC(O)C₆F₅]₂ (2)  with a yield of 85 %, from tris(m-tolyl)antimony with 2,3,4,5-tetrafluorobenzoic and pentafluorobenzoic acids in the presence of tert-butyl hydroperoxide (1:2:1 mol.). The structure of compounds 1 and 2 was established by the X-ray method performed on a Bruker D8 QUEST diffractometer. Crystallographic parameters of the unit cell of compound 1: the crystal size is 0.65 × 0.22 × 0.11 mm, a = 12.787(14), b = 12.957(19),
c = 13.726(16) Å, α = 64.27(6)°, β = 88.18(4)°, γ = 69.13(6)°, V = 1894 (4) ų, ρ_calc = 1.507 g/cm³, Z = 2, space group P-1. In the crystal cell of dicarboxylate 1, there is a molecule of the solvent used for recrystallization (benzene). Parameters of the crystal of compound 2: the crystal size is 0.46 × 0.39 × 0.3 mm, a = 13.68(5), b = 14.03(3), c = 17.95 (4) Å, α = 104.75 (8)°,
β = 98.65 (11)°, γ = 102.66 (13)°, V = 3172 (15) ų, ρ_calc = 1.712 g / cm³, Z = 2, space group P-1. The crystal cell of compound 2 contains two crystallographically independent molecules. The antimony atoms in compounds 1, 2 have a distorted trigonal-bipyramidal coordination with carboxylate ligands in axial positions. In crystal 1 the carboxylate ligands are in the cis-position, whereas in crystal 2 they are in the trans-position. In the IR spectra of compounds 1, 2 the bands at 1653, 1637 cm ^–1  (1) and 1699, 1681 cm^–1 (2) can be attributed to valence vibrations of the C=O-groups. The intense bands in the region of 1400-1100 cm^–1 in the IR spectra of dicarboxylates 1,  2 can be attributed to the valence vibrations of C-F: 1483, 1369 cm^–1 for compound 1 and 1334, 1246 cm^–1 for compound 2.