721944-47-4Relevant articles and documents
Chiral Chlorobismutines Stabilized by the Intramolecular Coordination of an N,N-Dimethylamino Group: X-Ray Structure Analysis, Asymmetric Induction at the Bismuth Centre and Dynamic behaviour in Solution
Suzuki, Hitomi,Murafuji, Toshihiro,Matano, Yoshihiro,Azuma, Nagao
, p. 2969 - 2974 (2007/10/02)
Chiral chlorobismuthines 3 stabilized by intramolecular coordination of an N,N-dimethylamino group have been synthesized by the selective fluorodearylation of the bismuthines 1 with boron trifluoride-diethyl ether, followed by halogen exchange of the resulting fluorobismuthines 2 with brine.An X-ray crystallographic structure analysis of 3b revealed that the bismuth centre has a distorted pseudotrigonal bipyramidal structure through the formation of a hypervalent 3-centre 4-electron bond with the chlorine and nitrogen atoms at apical positions. 1H NMR spectra of compounds 3 in CDCl3 at room temperature reflected their fixed conformation in the solid state.Chiral chlorobismuthines 7a and 7b were obtained in a similar manner starting from optically pure (R)-N,N-dimethyl-1-phenylethylamine as mixture of two diastereomers (77:23 and 78:22, respectively), the isomeric ratios of which were not influenced by the equatorial aryl group present.Variable-temperature dynamic 1H NMR spectra of the diastereomeric mixture of 7a provided important information about its behaviour in solution; in toluene dynamic but reversible dissociation of intramolecular Bi-N coordination was observed only at elevated temperatures, while in -DMSO it occured quite easily below room temperature, leading to the inversion of configuration at the chiral bismuth centre.
