Relationship between the Bowl-Shaped Geometry of Phosphangulene and an Axial Group on the Phosphorus Atom

Phosphangulene derivatives having various substituents on the phosphorus atom, which featured a bowl geometry and restrained bond angle, were synthesized in order to shed light on the relationship between the bowl geometry and the substituent. X-ray analysis revealed that the bowl geometry is significantly dependent on the axial group. An NBO analysis suggested that the bowl geometries become deep as the s-orbital character of the phosphorus orbital in the P–X bonds increases. The NMR, IR, CV, and DFT showed the large s-character in the P–X bonds of the phosphangulene lone pair.