Synthesis and molecular structure of boron-bridged constrained geometry complexes of zirconium and hafnium

The boron-bridged constrained geometry complexes [M{η5:η1-(C5H4)B(NiPr2)NPh}(NMe2)2] (M = Zr (1), Hf (2)) and [Zr{η5:η1-(C9H6)B(NiPr2)NPh}(NMe2)2] (3) have been prepared by reaction of the respective neutral ligand precursors (η1-C5H5)B(NiPr2)N(H)Ph and (1-C9H7)B(NiPr2)N(H)Ph with [M(NMe2)4] (M = Zr, Hf) with elimination of two equivalents of HNMe2. All new compounds have been characterised by means of multinuclear NMR spectroscopy and X-ray diffraction experiments.