Linkage Isomerism Leading to Contrasting Carboboration Chemistry: Access to Three Constitutional Isomers of a Borylated Phosphaalkene

We describe the reactivity of two linkage isomers of a boryl‐phosphaethynolate, [B]OCP and [B]PCO (where [B]=N,N’‐bis(2,6‐diisopropylphenyl)‐2,3‐dihydro‐1H‐1,3,2‐diazaboryl), towards tris‐ (pentafluorophenyl)borane (BCF). These reactions afforded three constitutional isomers all of which contain a phosphaalkene core. [B]OCP reacts with BCF through a 1,2 carboboration reaction to afford a novel phosphaalkene, E‐[B]O{(C(6)F(5))(2)B}C=P(C(6)F(5)), which subsequently undergoes a rearrangement process involving migration of both the boryloxy and pentafluorophenyl substituents to afford Z‐{(C(6)F(5))(2)B}(C(6)F(5))C=PO[B]. By contrast, [B]PCO undergoes a 1,3‐carboboration process accompanied by migration of the N,N’‐bis(2,6‐diisopropylphenyl)‐2,3‐dihydro‐1H‐1,3,2‐diazaboryl to the carbon centre.