The triphenylphosphonium methylenetriphenylphosphorane cation ( 1 ) has been shown to be mesomeric. A number of salts possessing this stable cation have been synthesized, including the inner salt triphenylphosphoniurntriphenylboronyl methylenetriphenylphosphorane (11). The photochromism of triphenylphosphonium methylenetriphenylphosphorane tetraphenylboron ( 12) is described.Recent investigation^^-^ of the reaction of triphenylphosphine with methylene bromide have led to the discovery of stable salts possessing the triphenylphosphoilium niethylenetriphenylphosphorane cation (la-c). I CA number of new salts of this type have been prepared and the previously assumed mesomeric nature of the cation has been confirmed.The essential precursor in the synthesis work was niethylenebis(triphenylphosphonium bromide) (2)which was prepared by the reaction of triphenylphosphine with methylene bromide or bromomethyltriphenylphosphonium bromide (3) in molten triphenylphosphate. The corresponding diphosphoniuni chloride (4) and iodide (5) could then be prepared by metathesis reactions of 2. These acidic salts were easily dehydrohalogenated with aqueous bases or n-butyllithiuin in hexane to produce triphenylphosphonium niethylenetriphenylphosphorane salts. Triphenylphosphoniuni methylenetriphenylphosphorane chloride (7) was also prepared by the reaction of hexaphenylcarbodiphos-phorane2p5 (8) with hydrochloric acid. Metathesis of triphenylphosphoniuni methylenetriphenylphosphorane bromide (6) gave an alternate route to the iodide (9). The bromide (6) and chloride (7) formed stable complexes with ferric chloride. The iodide (9) gave a triiodide coniplex (10) on reaction with iodine. Scheme I summarizes these reaction paths.Both physical and chemical evidence indicate that the triphenylphosphonium niethylenetriphenylphosphorane cation is better represented by the symmetrical mesomeric structure IC than by an ylide form. The phosphorus atoms in the cation were shown to be equivalent by the presence of a single P3I n.1ii.r. absorption (Table I). Additionally, the single, nonaromatic proton absorption appeared as a triplet, the nature of (1) This work was sponsored in part b y the Office (A) Hexaphenylcarbodiphosphorane ( 8 ) is triboluminescent. When crystals of 8 are crushed in a dry, nitrogen atmosphere, a green-white light flash is emitted from the compound.12, X R(CsH,)4 13, X = BFd 14, X = BH4 + (6) The synthesis of the nonrnesomeric inner salt (C&b)aP-CHg-f3(CsHa)s has been reported b y D. Seyferth and S. 0. Grim [ J . Am. C h r m . Soc., 83, 1613 (1961)l.

No abstract

No abstract

No abstract

No abstract