Formation of borata-alkene/iminium zwitterions by ynamine hydroboration†
Abstract
The ynamine TMP–CC–CH3 adds HB(C6F5)2 to give the unsaturated C2-bridged N/B FLP 5. Compound 5 shows the structural data indicating a marked participation of the zwitterionic mesomeric borata-alkene/iminium form. It splits dihydrogen at r.t. with Z- to E-isomerization at the central C
C double bond. Hydroboration of the ynamine Me3Si–C
C–NiPr2 with HB(C6F5)2 yields a N/B FLP that shows a strongly distorted central C
C double bond with a rotation of the planes of the substituent pairs at its ends by ca. 57°.