Oxabismoles and derivatives

Oxabismoles refer to a type of bismuth alkoxide in which the bismuth-oxygen bond is incorporated into the bismole ring system. Most known oxabismoles are benzoxabismoles as reported by Akiba et al., the unique ring system being stabilized by the Martin ligand. The general synthetic pathway to benzoxabismoles and their derivatives is shown below [930M1857]. 

Halogenolysis of pentacoordinated benzoxabismoles substituted differently by sulfuryl chloride discloses the following reactivity order of the bismuth-carbon bonds PhC=C-Bi Me-Bi Tol-Bi 4-CF3C6H4-Bi [930M1857]. 

A tetracoordinated organobismuth ate complex 44 (lO-Bi-4) has also been synthesized. Its structure characterized by X-ray crystallography shows that the bismuth atom has a distorted pseudotrigonal bipyramidal configuration, where the apical positions are occupied by two oxygen atoms [92TL6653], The equatorial plane is occupied by two carbon atoms and a lone pair of electrons. The apical Bi-O bond lengths (2.273 and 2.306 A) are remarkably shorter than the sum of the van der Waals radii (3.74 A) and approximate to that of the covalent radii (2.18 A). 

The reaction of potassium salt of the ate complex with sulfuryl chloride affords the pentacoordinated chlorobismuthorane 45 (lO-Bi-5) almost quantitatively. 

The introduction of two Martin ligands onto the bismuth center enhances considerably the stability of hexacoordinated ate complexes [89TL953, 930M3297], A thermally stable spirocyclic 12-B1-6 ate complex 49 is obtained and its dynamic behavior in solution has been characterized by variable temperature F-NMR spectra. 

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