The Oxidative-Addition Reactions of Tri(meta-tolyl)antimony and Tri(ortho-tolyl)antimony with 5-Nitrofurfuraldoxime in the Presence of Peroxides. The Molecular Structures of μ2-Oxo-bis[(5-Nitrofurfur-aldoximato)tri(meta-tolyl)antimony] and μ2-Oxo-bis[(5-Nitrofurfuraldoximato)tri(ortho-tolyl)antimony]

The interaction of tri(meta-tolyl)antimony and tri(ortho-tolyl)antimony with 5-nitrofurfural oxime in the presence of an oxidizing agent (hydrogen peroxide or tert-butyl hydroperoxide) leads to the formation of bis(5-nitrofurfuraldoximato)tri(meta-tolyl)antimony (1), μ2-oxo-bis[(5-nitrofurfuraldoximato)tri(meta-tolyl)antimony] (2), bis(5-nitrofurfuraldoximato) tri(ortho-tolyl)antimony (3) and μ2-oxo-bis[(5-nitrofurfuraldoximato)tri(ortho-tolyl)antimony] (4). The molecular structures of complexes 2 and 4 have been determined by X-ray diffraction analysis.

Oximes that contain two donor atoms (O and N) are ampolydentate ligands. However, according to X-ray diffraction data, the ligands of such antimony derivatives as Ar 3 Sb(ОNCRR') 2 and (Ar 3 SbОNCRR') 2 О are usually bound to the antimony atom only via the oxygen atom. In this case, short distances between the antimony atom and the nitrogen atoms of iminoxy-groups, which do not lead to the significant distortion of the trigonal-bipyramidal central atom coordination, are observed [11]. Sometimes the oxime ligand coordination method can be dependent on the nature of the aryl radicals at the antimony atom. For example, furfuraldoxime or 2-hydroxybenzaldoxime performs various structural functions in the derivatives of triphenyl- [8] and tri (o-tolyl) antimony [10] or triphenyl-and tris(5-bromo-2-methoxyphenyl)antimony [9], respectively.
Obviously, the oxidative-addition reactions of triarylantimony with oximes and the structure of the obtained products require further study.
The present work concerns the investigation of the interaction between tri(m-tolyl)-or tri(otolyl)antimony and 5-nitrofurfuradoxime in the presence of an oxidizing agent (hydrogen peroxide or t-butyl hydroperoxide) and the establishment of the product molecular structures. (1). 100 mg of tri(m-tolyl)antimony (0.25 mmol) and 79 mg (0.5 mmol) of 5-nitrofurfuraldoxime were dissolved in the mixture of diethyl ether (15 mL) and heptane (15 mL), then 28 mg of 30 % aqueous solution of hydrogen peroxide (0.25 mmol) were added. The mixture was kept for 24 hours at 20 °C. After the solvent evaporation, the light-yellow crystals of 1 were obtained (m = 0.132 g (78 %), MP = 78 °C).
Data collection and editing, the refinement of unit cell parameters, and correction for absorption were carried out in SMART and SAINT-Plus software [10]. All calculations aimed at solving and refining the structures of 2, 4 were performed in SHELXL/PC software [11]. The structures of 2, 4 were determined using direct methods and refined with LS method in the anisotropic approximation for nonhydrogen atoms. The selected crystallographic data and the structure refinement results are listed in Table 1. Selected bond lengths and bond angles are summarized in Table 2.

Results and Discussion
We have studied the reactions of tri(m-tolyl) -and tri(o-tolyl)antimony with 5-nitrofurfuraloxime at various molar ratios in the presence of an oxidizing agent. It has been found that at molar ratio 1: The synthesized triarylantimony dioximates have been identified by infrared spectroscopy and X-ray diffraction analysis.
According to the X-ray diffraction analysis data, the antimony atoms in the molecules of compounds 2 and 4 have distorted trigonal-bipyramidal coordination with oxygen atoms in axial positions (Fig. 12). Molecule 4 is centrosymmetric. In binuclear molecules 2, 4 the Sb (1) and Sb (2) atoms are connected by the bridging oxygen atom, Sb The structure organization of crystals 2, 4 is due to weak intermolecular О··· n the oxygen atoms of nitro groups and the hydrogen atoms of methyl groups or aromatic rings, interactions.
The structure of the products of the reactions of tri(m-tolyl)-and tri(o-tolyl) antimony with nitrofurfuraldoxime depends on the molar ratio of the reactants. Regardless of the nature of the oxidant, the reaction of triarylantimony with 5-nitrofurfuraloxime at molar ratio 1:2 leads to the formation of tritolylantimony dioxymates. At the stoichiometric ratio of the reagents the antimony organic product with the bridging oxygen atom is formed.
The structure of molecules is determined by the aryl radical nature, thus, the tolyl)antimony molecule] has the angular structure of the central fragment, nitrofurfuraldoximato)tri(o-tolyl) antimony] molecule is centrosymmetric and has a linear structure. The oxime ligands are monodentate in both cases; they are bound to the antimony