Structural study on the organoantimony(III) NCN – Chelated compounds [2,6-(Me 2NCH 2) 2C 6H 3]SbX 2 – Influence of the polar group X

Abstract

The reactions of organoantimony chloride LSbCl 2 ( 1) (L = [2,6-(Me 2NCH 2) 2C 6H 3] −) with the silver salts of selected carboxylic acids (1:2 molar ratio) resulted to the corresponding organoantimony carboxylates LSbX 2, where X = CH 3COO for ( 2); CF 3COO for ( 3). Similar reactions of 1 with the silver salt of the low nucleophilic CB 11 H 12 - anion (1:0.5 and 1:1 molar ratio) gave the ionic compounds [LSb(Cl)--Cl–Sb(Cl)L] +[CB 11H 12] − ( 4), and [LSbCl] +[CB 11H 12] − ( 5). All compounds were characterized by the help of the elemental analysis, ESI-MS, 1H, 11B, 13C NMR spectroscopy and IR spectroscopy. The solid state structure investigation using single crystal X-ray diffraction technique ( 3–5) revealed the presence of the strong Sb–N intramolecular dative connections in all cases and also significant differences in the shapes of the coordination polyhedra around the central antimony atoms was observed, i.e. a tetragonal pyramidal environment in 3 (CF 3COO groups are placed mutually in trans positions), an unusual chlorine bridged dinuclear cation consisting of one apex (Cl atom) sharing square pyramids in 4, and finally a vacant ψ-trigonal bipyramid around the central antimony atom in 5. Even more, crystallization of 5 from THF provided the single crystals of a THF aduct of 5 [LSbCl(THF)] +[CB 11H 12] − 5a, where the central antimony atom is located in a tetragonal pyramidal environment. The solid state structures of 3– 5 are retained in solution. Solution structure of the compound 2 was determined by the help of VT- 1H NMR spectroscopy and IR spectroscopy showing, that both carboxylates (CH 3COO) are unidentate and are placed mutually in cis positions in the coordination polyhedron around the central antimony atom. The whole coordination polyhedron in 2 might be best described as a biccaped – trigonal pyramid, due to the additional Sb–N intramolecular interactions.