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)(eta(6)-1,2-F2C6H4)][Al{OC(CF3)(3)}(4)] and [Rh(dcpm)(eta(6)-1,2,3-F3C6H3)][Al{OC(CF3)(3)}(4)]. These complexes act as precursors to a previously inaccessible sigma-amine-borane complex [Rh(dcpm)(eta(2)-H3B center dot NMe3)][Al{OC(CF3)(3)}(4)] of a small bite-angle phosphine. This complex is a poor catalyst for the dehydrocoupling of H3B center dot NMe2H. Instead, formation of the bridging borylene complex [{RhH(mu-dcpm)}(2)(mu-H)(mu-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.