Electrophilic bis-fluorophosphonium dications: Lewis acid catalysts from diphosphines

Stepwise oxidation of 1,8-bis(diphenylphosphino)naphthalene and a series of (oligo)methylene-linked diphosphines with XeF(2) followed by fluoride abstraction yields a family of compounds featuring phosphine, phosphonium and phosphorane moieties in close proximity. The bisphosphonium ions [(C(10)H(6))(Ph(2)PF)(2)](2+) (5) and [CH(2)(Ph(2)PF)(2)](2+) (9a) exhibit remarkable Lewis acidity arising from the proximity of the phosphonium centers. The effectiveness of bisphosphonium dications (5, 9a–e) is examined in a series of Lewis acid catalysed transformations.