Structures, dynamic behaviour, and reactivity of P-cyclopentadienyl-substituted 1,3,2-diazaphospholenes

Abstract

P-Cyclopentadienyl-substituted 1,3,2-diazaphospholenes were prepared by salt metathesis from NaCp or LiCp* and 2-chloro-1,3,2-diazaphospholenes. Comprehensive spectroscopic and X-ray diffraction studies revealed a significant lengthening of the phosphorus–carbon bonds as compared with typical P–C bond distances, and the presence of fluxional molecular structures in solution and solid state as a consequence of circumambulatory migration of the diazaphospholene moiety around the Cp-ring. The P–C bond lengthening is accompanied by the capability to react with transition metal complexes under P–C bond activation and cyclopentadienyl transfer. At the same time, 2-Cp-diazaphospholenes react with strong bases under deprotonation to afford a phosphinyl–cyclopentadienide anion that reacts further with FeCl₂ to a 1,1′-bisphosphinyl–ferrocene. The ambivalent behaviour of the diazaphospholenes offers interesting prospects to develop new synthetic methods for functional cyclopentadienyl complexes.