Strong metal-borane interactions in low-valent cyclopentadienyl rhodium complexes

The first examples of half-sandwich Rh(i) complexes stabilized by borane coordination have been prepared and structurally characterized. As substantiated by NMR spectroscopy and single-crystal X-ray diffraction, the phosphine-borane ligand iPr(2)P-(o-C6H4)-BFxyl(2) 1 [Fxyl = 3,5-(F3C)(2)C6H3] engages in tight eta (3)-BCC or eta (1)-B coordination, depending on the metal environment.