Phosphino-Boryl-Naphthalenes: Geometrically Enforced, Yet Lewis Acid Responsive P → B Interactions

Three
naphthyl-bridged phosphine-borane derivatives 2-BCy2, 2-BMes2, and 2-BFlu,
differing in the steric and electronic properties of the boryl moiety,
have been prepared and characterized by spectroscopic and crystallographic
means. The presence and magnitude of the P → B interactions
have been assessed experimentally and theoretically. The naphthyl
linker was found to enforce the P → B interaction despite steric
shielding, while retaining enough flexibility to respond to the Lewis
acidity of boron.