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Synthesis and structure of triarylantimony dioximates

“…The presence of an intramolecular Sb...N contact in compounds I and II does not significantly affect the equatorial angles which only slightly differ from the theoretical value of 120o, unlike what is observed in triarylantimony dicarboxylates, where intramolecular Sb...O=C contacts much increase one of the equatorial angles (143.83151.7o) [22328]. Bidentate ligation of the oximate ligand was observed in all previously structurally characterized tri-and tetraarylantimony oximates [5,7,8,15,19].…”

“…In other structurally characterized triarylantimony dioximates, the Sb3C and Sb3O bond lengths span the ranges 2.09732.120 and 2.04432.080 A [7,8,16], i.e. here, too, violation of the abovementioned rule takes place.…”

“…The Sb3O bond length in triarylantimony dioximates [7,8] is close to the sum of the covalent radii of Sb and O, which ensures interaction between Sb and the oximate nitrogen. The fact that the Sb...N distances in triarylantimony dioximates are much shorter than those expected by the van der Waals radii points to strong intramolecular donor3acceptor interactions in these compounds, which may be one of the reasons for their stability.…”

“…Ph 4 SbON=CPh 2 + HON=CPh 2 76 Ph 3 Sb(ON=CPh 2 ) 2 + PhH. (8) To gain insight into structural features of triarylantimony dioximates, we performed an X-ray diffraction analysis of triphenylantimony bis(5-bromo-2-hydroxybenzaldoximate) (I) and tri-p-tolylantimony bis(cyclohexanone oximate) (II) (Figs. 1 and 2).…”

“…length in triarylantimony dioximates is close to the sum of the covalent radii of antimony and oxygen (2.07 A [21]), being considerably smaller than in triarylantimony dicarboxylates ( Note that the geometric parameters of tri-p-tolylantimony bis(cyclohexanone oximate) (II) and triphenylantimony bis(cyclohexanone oximate) [8], as well as of tri-p-tolylantimony bis(acetophenone oximate) [8] and its phenyl analog [7] practically do not differ from each other, implying a weak effect the electron-donor methyl groups in the aryl ligands on the antimony atom exert on the geometry of these molecules.…”