Crystal structure of the phosphanylidene-sigma(4)-phosphorane DmpP=PMe3 (Dmp=2,6-Mes(2)C(6)H(3)) and reactions with electrophiles

The stable phosphanylidene-sigma(4)-phosphorane DmpP=PMe3 (1, Dmp = 2,6-Mes (2)C(6)H(3)) has been examined by single-crystal X-ray diffraction methods. The structure of 1 features a relatively short P-P bond length of 2.084(2) Angstrom. Reactions of 1 with various electrophiles demonstrate the nucleo philic behavior of the phosphanylidene atom of 1 and also provide access to new organophosphorus compounds. For example, addition of excess BH3 (in th e form of either BH3. THF or BH3. SMe2 to 1 leads to formation of a mono-bo rane adduct DmpP(BH3)PMe3. Reactions of carbon and silicon based electrophi les EX (E = R3C or R3Si; X = halide or OTf-) produce either diphosphanium s alts [DmpP(E)PMe3]X or phosphines DmpP(E)X. In some cases equilibrium mixtu res of both product types are observed, and the equilibria can be shifted b y addition of either X- or PMe3. Compound 1 is also readily protonated by H OTf, HCl and PhOH. As found for the carbon and silicon based electrophiles, the nature of the resulting product depends on the counterion. (C) 2000 El sevier Science S.A. All rights reserved.