Synthesis and Identification of Aryl and Alkyl Gem-Dilithium Phosphido-Boranes: A Boost to the Chemistry of Phosphandiides
Résumé
The synthesis and identification of unprecedented gem‐dianionic phosphorus compounds, that is, gem‐dilithium phosphido‐boranes Li2[RP⋅BH3], with R=Ph or Cy, are reported in THF solution. These were obtained by double deprotonation of the corresponding primary phosphine‐borane precursors RPH2⋅BH3. Their in‐depth structural study, based on multinuclear (1H, 6Li, 7Li, 11B, 13C, 31P) mono‐ and bi‐dimensional NMR analyses, indicates a strong influence of the phosphorus substituent on the structure of the gem‐dianionic phosphorus structure; a monomeric arrangement was obtained when R=phenyl, whereas a cyclic oligomer was observed for R=cyclohexyl. These compounds represent a new type of useful reagent, and their access paves the way for the concept of “RP synthons” (i.e., RP2− phosphandiides), likely to be the most flexible precursors of a variety of phosphorus targets.