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.

Boravinylidenes are intermediates in 1,1-hydroboration reactions of alkynes en route to vinyl boranes. Unlike transition metal-vinylidene complexes, boravinylidenes have hitherto, not been crystallogr...