Reactions of Borafluorene with Iminophosphines: PN Insertion and Skeletal Editing to Phosphafluorene

The reactions of iminophosphines (Mes*N=PR, Mes* = 2,4,6-tri-tert-butylphenyl) with 9-phenyl-9-borafluorene resulted in the isolation of two distinct products. For an iminophosphine bearing a phenyl group on phosphorus, a seven-membered BNPC4 ring was isolated, while for the chloride variant, an unusual boracycle to phosphacycle transformation was observed to generate a phosphafluorene. Density functional theory (DFT) computations provide mechanistic insights, which indicate that the lability of the P–Cl bond and resiliency of the P–Ph unit influence the reaction pathways.