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

Three naphthyl-bridged phosphine-borane derivatives 2-BCy2, 2-BMes(2) and 2-BFlu, differing in the steric and electronic properties of the boryl moiety, have been prepared and characterized by spectroscopic and crystallo-graphic 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.