Synthesis and Crystal Structure of Tris(3-fluorophenyl)antimony Bis(2-methylcarboranylcarboxylate)

Abstract—

Oxidation of tris(3-fluorophenyl)antimony with tert-butyl hydroperoxide in the presence of 2-methylcarboranylcarboxylic acid leads to the formation of tris(3-fluorophenyl)antimony bis(2-methylcarboranylcarboxylate) (1), whose structural features were established by X-ray diffraction analysis. According to X-ray diffraction analysis carried out at 293 K using a D8 Quest Bruker automatic four-circle diffractometer (two-coordinate CCD detector, MoK_α radiation, λ = 0.71073 Å, graphite monochromator), crystals are characterized as follows: C₂₆H₃₈B₂₀F₃O₄Sb, M 809.52; monoclinic syngony, symmetry group С2/c; cell parameters: a = 19.050(13) Å, b = 14.441(9) Å, c = 14.568(9) Å; α = 90°, β = 98.51(2)°, γ = 90°; V = 3964(4) ų ; Z = 4; crystal size 0.8 × 0.55 × 0.29 mm; reflection index intervals –25 ≤ h ≤ 25, –18 ≤ k ≤ 18, –18 ≤ l ≤ 19; total reflections 37 401; independent reflections 4709; R_int 0.0545; GOOF 1.108; R₁ = 0.0578, wR₂ = 0.1482; residual electron density –0.59/1.09 e /ų. According to the X-ray diffraction data, the antimony atoms in the molecules of compound 1 have a distorted trigonal-bipyramidal coordination with oxygen atoms of the carboxylate ligands in axial positions. The Sb–C bonds (2.104(4)–2.114(8) Å) are shorter than the Sb–O distances (2.113(3) Å), the OSbО axial angle is 178.48(15)°, the CSbC angles are 109.7(2)°, 118.4(2)°, and 131.8(3)°. The significant increase in one of the angles is associated with the cis-conformation of carboxylate ligands relative to the equatorial plane. There is a propeller conformation of aryl ligands with respect to the equatorial plane [C₃]. Structure 1 contains intramolecular Sb···O=C contacts between the antimony and oxygen atoms of the carbonyl groups of the carboxylate ligands, which are 3.089(3) Å. The formation of a spatial network in the crystal of compound 1 is due to the presence of weak hydrogen bonds carboxylate ligands and fluorine aryl ligands with the participation of boron atoms: B···H (3.19 Å) and F···B (3.45 Å). Complete tables of atomic coordinates, bond lengths, and bond angles have been deposited with the Cambridge Crystallographic Data Center (no. 2178731; deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/data_request/cif).