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Synthesis and structure of bis(tetraphenylantimony) malonate* I. V. Egorova, V. V. Zhidkov, I. N. Zubakina, and N. A. Rodionova Blagoveschensk State Pedagogical University, 104 ul. Lenina, 675000 Blagoveschensk, Russian Federation. Fax: +7 (416) 252 4164. E-mail: [email protected] Bis(tetraphenylantimony) malonate was synthesized by the reaction of tetraphenylantimony bromide with silver malonate (the molar ratio was 2  :  1) in toluene. According to the X-ray diffraction data, the tridentate carboxylate ligand is a chelate. The coordination number of the Sb(1) atom involved in a contact with the carbonyl oxygen atom increases to six (Sb(1)—O(1), 2.199(7) Å; Sb(1)—O(3), 2.362(7) Å). Another antimony atom remains five-coordinate (Sb(2)—O(4), 2.304(7) Å). The antimony atoms Sb(1) and Sb(2) have distorted octahedral and trigonal-bipyramidal coordination geometry, respectively. Key words: tetraphenylantimony bromide, bis(tetraphenylantimony) malonate, X-ray diffraction, chelating carboxylate ligand.

"A unique feature of organoelement and organometallic compounds is high sensitivity to the local chemical environment, which allows for fine optimization of their properties by selecting appropriate ligands."1 The synthesis of SbV organic compounds and their structure determination have attracted attention due to their great synthetic potential. Organoantimony compounds exhibit O- and N-arylating ability toward primary and secondary amines, alcohols, and phenols, are used in the synthesis of dipeptides, and react with aldehydes to form addition products, the hydrolysis of which affords the corresponding alcohols.2—8 Organoantimony compounds display catalytic activity in the synthesis of amides, substituted ureas, carbocyclic esters, imidazolidin-2-ones, carbodiimides, polyesters, thiocarboxylic acids, and cyclic carbonates, polymerization reactions of alkene oxides, and condensation of oxiranes.9—18 Triarylantimony(V) amides and carboxylates exhibit insecticidal, antibacterial, and anticancer activity.19—23 Polymer films based on metal mono- and polycarboxylates have improved mechanical, adhesion, optical, and electrical properties.24—28 Among antimony(V) carboxylates, compounds of the general formulas Ar4SbX and Ar3SbX2, where X is a monocarboxylic acid moiety, were structurally most wellcharacterized. The presence of a carboxyl group in tetraand triarylantimony acrylates promotes an additional intramolecular coordination of the central atom by the carbonyl oxygen atom (Sb···O) and an increase in the coordination number of the antimony atom to 6 or 7. Mean*  Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).

while, the structures of organoantimony compounds of the general formula (R4Sb)2L, where L is a dicarboxylic acid moiety, were studied for a small number of examples.29 Investigations of the crystal structures of bis(tetraorganylantimony) carboxylates started with the structure determination of derivatives of the first represen