Synthesis, halogenolysis, and crystal structure of hypervalent organobismuth compounds (10-Bi-5)

Article abstract of DOI:10.1021/om00029a047

The stable 10-Bi-5 compounds (o-C₆H₄C(CF₃)₂O)BiAr₂R (3, (Ar, R): 3a, p-CH₃C₆H₄,p-CH₃C₆H ₄; 3b, p-CF₃C₆H₄, p-CF₃C₆H₄; 3c, p-FC₆H₄, p-FC₆H₄; 3d, p-CH₃C₆H₄, p-CF₃C₆H₄; 3e, p-CF₃C₆H₄, p-CH₃C₆H₄; 3f, p-CH₃C₆H₄, PhC≡C; 3g, p-CH₃C₆H₄, Me) were synthesized. The X-ray structures of 3a,f,g showed distorted-trigonal-bipyramidal geometries, and the electronegative apical PhC≡C ligand of 3f made the apical Bi-O bond (2.243(3) ?) shorter than the Bi-O bond of 3a,g (2.323(4) ? in 3a and 2.328(7) ? in 3g). Halogenolysis of 3 with sulfuryl chloride or pyridinium bromide perbromide gave the five-coordinate bismuth compounds (o-C₆H₄C(CF₃)₂O)BiAr ¹-Ar²X(6 (Ar¹,Ar²,X): 6a, p-CH₃C₆H₄, p-CH₃C₆H₄, Cl; 6b, p-CF₃C₆H₄, p-CF₃C₆H₄, Cl; 6c, p-FC₆H₄, p-FC₆H₄, Cl; 6d, p-CH₃C₆H₄, p-CH₃C₆H₄, Br; 6e, p-CH₃C₆H₄, p-CF₃C₆H₄, Cl; 6f, p-CH₃C₆H₄, p-CF₃C₆H₄, Br) in good to quantitative yield with apical covalent Bi-halogen bonds which were clearly shown by the X-ray analysis of 6a,b,d,e. The reactivity order of 3 for the halogenolysis was as follows: PhC≡C-Bi> Me-Bi> p-CH₃C₆H₄-Bi> p-CF₃C₆H₄-Bi. Direct halogenolysis of the bismuth-carbon bond was suggested. The variable-temperature ¹⁹F NMR of unsymmetrically substituted 6e,f did not show coalescence of the CF₃ groups up to 170°C in a dilute solution of toluene-d₈, and the energies of inversion at the bismuth atom should be higher than 21 kcal mol^-1 at 170°C.