Organobismuth(III) Dihalides with T-Shaped Geometry Stabilized by Intramolecular N→Bi Interactions and Related Diorganobismuth(III) Halides

Organobismuth(III) compounds containing ( N,C,N )-pincer ligands were prepared and characterized both in solution and in the solid state. Compound RBiCl 2 1 [R = 2,6-(Me 2 NCH 2 ) 2 C 6 H 3 ] was obtained from RLi and BiCl 3 (1:1 molar ratio). RBiBr 2 2 and RBiI 2 3 were obtained by halogen-exchange reactions from 1 . Reaction of 1 with MeMgI afforded RBi(Me)I 4 . Compound R 2 BiCl 5, obtained from RLi and BiCl 3, is rearranged in solution to 1 and R 3 Bi. The molecular structures of compounds 1 − 5 were established by single-crystal X-ray diffraction. All dihalides RBiX 2 show a T-shaped CBiX 2 core. They are the first stable compounds corresponding to the edge inversion “transition state” at the bismuth center, stabilized by two strong intramolecular N→Bi interactions in trans positions to each other, which contribute to an overall distorted square pyramidal ( N,C,N )BiX 2 coordination geometry. The electronic structure of [2,6-(Me 2 NCH 2 ) 2 C 6 H 3 ]BiCl 2 ( 1 ) was analyzed by density functional theory (DFT) calculations, which provide evidence that the stabilization of the square pyramidal geometry of bismuth is electronic rather than steric in nature.