ja0399019_si_002.cif (18.94 kB)

The Tetra(vinyl)phosphonium Cation [(CH2CH)4P]+

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posted on 18.02.2004, 00:00 by Uwe V. Monkowius, Stefan D. Nogai, Hubert Schmidbaur
A convenient high-yield synthesis of tetra(vinyl)phosphonium salts is presented, based on the hydrophosphination of PH3 with vinyl acetate, the quaternization of the first intermediate by 2-iodoethanol, followed by its acetylation, and in the crucial final step by careful elimination of 4 equiv of acetic acid. The intermediates and products have been characterized by their analytical and spectroscopic data, and the crystal structure of the tetraphenylborate salt [Vi4P]+ [BPh4]- has been determined. The ground-state conformation of the cation is of low symmetry (point group C1, with three vinyl groups forming a propeller), as confirmed by quantum chemical calculations. This structure has now also been found for the [BVi4]- anion in its methyltriphenylphosphonium salt, or, previously, for tetravinylmethane and -silane, and appears to be general for tetravinylelement species. By contrast, tetra(ethyl)element molecules, cations or anions [Et4E] generally feature S4 symmetry. Alkyltrivinylphosphonium salts [RPVi3]+ X- are available following a similar procedure as demonstrated for the cyclohexyl series (R = Cy).