Isolable C-Phosphonio-Boratavinyl Anion

A persistent C-phosphonio boratavinyl anion 1 has been successfully synthesized. This boron-containing vinyl-lithium 1, featuring a vinyl carbon with a negative charge (-1.59), considerably higher than that of carbon analogue 7 (-0.76), exhibits strongly nucleophilic and basic properties, as demonstrated by the results of rapid reactions with H₂ (10 bar, 15 min or 1 bar, 2 h at RT) and C₆F₆ (1 equiv., 15 min at -80°C). The reactions of boratavinyl anion 1 with electrophiles offer a convenient route for the introduction of a borata-alkene-based bulky and σ,π-double-donating substituent, enabling to efficiently stabilize reactive intermediates such as halogenogermylenes. Furthermore, the reaction with CO₂ takes place at the borata-alkene moiety, rather than at the P-ylide function, resulting in the double insertion of CO₂ into the B─C bond to afford a unique cyclic P-ylide 13.