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

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.