Crystal structure of the phosphanylidene-#sigma#~4-phosphorane DmP=PMe_3 (Dmp = 2,6-Mes_2C_6H_3) and reactions with electrophiles

摘要

The stable pbospbanylidene-cr4-pbospborane DmpP=PMe_3 (I, Dmp = 2,6-Mes_2C_6H_3) bas been examined by single-crystal X-ray diffraction methods. The structure of I features a relatively short P-P bond length of 2.084(2) A. Reactions of 1 with various electrophiles demonstrate the nucleophilic behavior of the phosphanylidene atom of 1 and also provide access to new organophosphorus compounds. For example, addition of excess BH_3 (in the form of either BH_3.THF or BH_3"SMe_2) to 1 leads to formation of a mono-borane adduct DmpP(BH3)PMe3. Reactions of carbon and silicon based electrophiles EX (E = R_3C or R3Si; X = halide or OTf-) produce either diphosphanium salts [DmpP(E)PMe_3]X or phosphines DmpP(E)X. In some cases equilibrium mixtures of both product types are observed, and the equilibria can be shifted by addition of either X- or PMe_3. Compound I is also readily prO;tonated by HOTf, HCI and PhOH. As found for the carbon and silicon based electropbiles, the nature of the resulting product de~nds on the counterion.