Fluoroarene Complexes with Small Bite Angle Bisphosphines:Routes to Amine–Borane and Aminoborylene Complexes

Fluoroarene complexes of the small bite angle bisphosphine Cy2PCH2PCy2 (dcpm) have been prepared: [Rh(dcpm)(η6-1,2-F2C6H4)][Al{OC(CF3)3}4] and [Rh(dcpm)(η6-1,2,3-F3C6H3)][Al{OC(CF3)3}4]. These complexes act as precursors to a previously inaccessible σ-amine–borane complex [Rh(dcpm)(η2-H3B·NMe3)][Al{OC(CF3)3}4] of a small bite-angle phosphine. This complex is a poor catalyst for the dehydrocoupling of H3B·NMe2H. Instead, formation of the bridging borylene complex [{RhH(µ-dcpm)}2(µ-H)(µ-BNMe2)][Al{OC(CF3)3}4] occurs, which has been studied by NMR, mass spectrometry, crystallographic and DFT techniques. This represents a new route to bridging borylene complexes.