Synthesis, Structure, and Reactivity of Group 4 Metallacarboranes Bearing the Ligand [Me<sub>2</sub>C(C<sub>9</sub>H<sub>6</sub>)(C<sub>2</sub>B<sub>9</sub>H<sub>10</sub>)]<sup>3−</sup>
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The new inorganic/organic hybrid ligand [NMe3H][Me2C(C9H7)(C2B9H11)] was prepared via a selective deboration of Me2C(C9H7)(C2B10H11) with piperidine in ethanol. Reaction of the ligand with Zr(NMe2)4 provided the neutral group 4 metal amide complex trans-[η5:η5-Me2C(C9H6)(C2B9H10)]Zr(NMe2)(NHMe2) (3) through an amine elimination reaction. Treatment of the trianionic salt of the ligand with MCl4(THF)2 gave the mixed sandwich complexes trans-[{η5:η5-Me2C(C9H6)(C2B9H10)}MCl2][Na(DME)3] (M = Zr (4), Hf (5)). Complex 4 reacted with KCH2Ph, C5H5Na, or NaNH(C6H3-2,6-Me2) to afford trans-[{η5:η5-Me2C(C9H6)(C2B9H10)}ZrCl(CH2C6H5)][Na(DME)3] (6), trans-{[η1:η5-Me2C(C9H6)(C2B9H10)]ZrCl(η5-C5H5)}{Na(DME)3} (7), or trans-[η5:η5-Me2C(C9H6)(C2B9H10)]Zr(NHC6H3Me2)(THF) (8), respectively. Both 6 and 7 were thermally stable, and no NaCl elimination was observed upon heating their DME solutions. Complex 4 also reacted with excess NaH in THF to generate the ring-opening product trans-[η5:η5-Me2C(C9H6)(C2B9H10)]Zr(OCH2CH2CH2CH3)(THF) (9). In the presence of excess MAO (methylalumoxane), complexes 3, 4, and 6 were active catalysts for ethylene polymerization. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Some were further confirmed by single-crystal X-ray analyses.
