Synthesis and structure of six-coordinated organobismuth compounds with bidentate ligands (12-Bi-6)

Article abstract of DOI:10.1021/om00032a060

The thermally stable 12-Bi-6 compound 3-Li⁺, {(o-C₆H₄C(CF₃)₂O) ₂}Bi(p-CH₃C₆H₄)₂ ^-Li⁺, was synthesized. ¹⁹F NMR of 3-Li⁺ showed a pair of quartets at room temperature but showed a singlet after addition of 12-crown-4 to the solution. The result indicated an important role of the Li⁺ on the structure of the ate complex, and the structure of the Li salt was assigned as 3A, bearing two cis oxygens, two cis p-tolyl groups, and two trans carbons at ligation sites about the central bismuth atom. The structure of the ate complex in the presence of 12-crown-4 was assigned as 3C, bearing two cis oxygens, two trans p-tolyl groups, and two cis carbons at ligation sites. Compounds 3 were stable up to 150°C, but the pair of quartets coalesced at 70 °C and the activation energy of the equilibrium between the CF₃ groups was calculated to be 18 kcal mol^-1 at 70°C. Bismuth-oxygen bond cleavage followed by pseudorotation was suggested for the coalescence. Compounds 3 were inert to electrophilic reagents such as p-(trifluoromethyl)benzoyl chloride. Water reacted with 3 to give an alcohol 17. The alcohol was unstable at room temperature and cyclized with elimination of toluene to afford a 10-Bi-5 (12). Intramolecularly coordinated 12-Bi-6 compounds 18, (o-C₆H₄C(CF₃)₂O)BiAr ₂(o-C₆H₄CR₂X) { Ar, R, X: 18a p-CH₃C₆H₄, CF₃, CH₃O; 18b p-CF₃C₆H₄, CF₃, CH₃O; 18c p-CH₃C₆H₄, H, (CH₃)₂N; 18d p-CF₃C₆H₄, H, (CH₃)₂N}, were synthesized, three of which were structurally determined by X-ray analysis. The structures were all cis geometry. The synthesis and stability of 12-Bi-6 ate complexes 5, (o-C₆H₄C(CF₃)₂O)Bi(p-CH ₃C₆H₄)₃R-Li⁺, were also described.