Weak Pnictogen Bond with Bismuth: Experimental Evidence Based on Bi-P Through-Space Coupling

Abstract

To study pnictogen bonding involving bismuth, flexible accordion-like molecular complexes of the composition [P(C₆ H₄ -o-CH₂ SCH₃ )₃ BiX₃ ], (X=Cl, Br, I) have been synthesised and characterised. The strength of the weak and mainly electrostatic interaction between the Bi and P centres strongly depends on the character of the halogen substituent on bismuth, which is confirmed by single-crystal X-ray diffraction analyses, DFT and ab initio computations. Significantly, ²⁰⁹ Bi-³¹ P through-space coupling (J=2560 Hz) is observed in solid-state ³¹ P NMR spectra, which is so far unprecedented in the literature, delivering direct information on the magnitude of this pnictogen interaction.

Keywords: ab initio calculations; bismuth; density functional calculations; noncovalent interactions; phosphorus; solid-state NMR spectroscopy.