From a Fluorenyl Substituted Ylide‐Functionalized Phosphine to a Neutral Phosphide via P−C Bond Cleavage

Abstract

Best wishes to Prof. Sjoerd Harder on the occasion of his 60th birthday Bulky ylide-substituted phosphines have recently found application as potent ligands in homogeneous catalysis. The attempted synthesis of the ylide-substituted fluorenylphosphine Y Ph P-(Cy)Flu [Y Ph = Cy 3 P(Ph)C; Flu = 9-methylfluorenyl] now resulted in the unexpected elimination of 9-methylenefluorene during the deprotonation step of the intermediary α-phosphino phosphonium salt to yield the secondary ylide-substituted phosphine Y Ph P(Cy)H. This phosphine underwent formal H 2 elimination under basic conditions to form a cyclic phosphonium ylide with a PÀ CÀ PÀ C four-membered ring via deprotonation of one cyclohexyl group of the PCy 3 moiety. Upon coordination to transition metals the secondary ylidylphosphine forms a neutral phosphide ligand by shift of the proton into the ylide-backbone and formation of zwitterionic metal complexes.

Rhodium(I) Complexes with a η1-Fluorenyl-P-phosphanylphosphorane Ligand

“…In conclusion, P-phosphination of L0 has produced the P -phosphanylphosphorane L2 , whose coordination to [Rh­(diene) 2 ]­BR 4 has given cyclorhodated complexes, containing a η 1 -coordinated fluorenyl ligand. 9-Fluorenyl is an electron-releasing, sterically demanding substituent that has produced phosphanes for catalysis. − The metalation of fluorene presented here should further increase electron donation and steric crowding to the metal. Additionally, it is likely that similar compounds with other substituents should be accessible.…”