Synthesis and structure of tri-para-tolylantimony bis(2-nitrobenzoate)

Tri-para-tolylantimony bis(2-nitrobenzoate) p-Tol3Sb(O2CC6H4-NO2-2)2 was first obtained by the reaction of tri-para-tolylantimony and ortho-nitrobenzoic acid in the presence of hydrogen peroxide at room temperature in a solution of THF or ether/isopropyl alcohol mixture for 1 day in the presence of air, yielding 76–89 %. The reaction of tri-para-tolylantimony with ortho-nitrobenzoic acid can also occur in the absence of hydrogen peroxide in argon at room temperature for 30 days, yielding p-Tol3Sb(O2CC6H4-NO2- 2)2 up to 80 %. The composition of the product has been confirmed by X-ray diffraction, 1H, 13C NMR, IR spectroscopy. The antimony atom has distorted trigonal bipyramid coordination, at the base of which there are three tolyl groups, the sum of the C15SbC22, C15SbC29, and C22SbC29 valence angles is 360°. The vertices of the bipyramid contain carboxylate groups, and the O1SbO3 valence angle is 173°. The value of the structural parameter τ is 0.64, indicating the presence of some contribution from the structure of a tetragonal monopyramid. The metal atom has an additional coordination of the donor-acceptor type with two carbonyl oxygen atoms. In the IR spectrum of the product, the difference between the vas(COO) and vs(COO) values is 294 cm-1, which indicates that the monodentate binding of the carboxylate groups to the Sb atom prevails over the bidentate one.