Cyclopentadienyl−Hydrazido Titanium Complexes:  Synthesis, Structure, Reactivity, and Catalytic Properties

An η1-hydrazido bis(dimethylamido) complex, [(η5-C5Me4)SiMe2(η1-NNMe2)]Ti(NMe2)2 (2), has been prepared from a neat reaction of (C5Me4H)SiMe2(NHNMe2) (1) with Ti(NMe2)4 at 130 °C via amine elimination. Treatment of 2 with Me3SiCl gives an η2-hydrazido dichloro compound, [(η5-C5Me4)SiMe2(η2-NNMe2)]TiCl2 (3). The reaction of 2 with excess AlMe3 (ca. 5 equiv) affords an AlMe3 adduct, [(η5-C5Me4)SiMe2(η1-NNMe2AlMe3)]TiMe2 (4), which is converted to a dimethyl complex, [(η5-C5Me4)SiMe2(η2-NNMe2)]TiMe2 (5), upon treatment with NEt3. The reaction of 5 with B(C6F5)3 affords a methyl−triarylborate complex, [(η5-C5Me4)SiMe2(NNMe2)]TiMe(μ-Me)B(C6F5)3 (6). The reaction of 2 with H2O produces a tetrameric organotitanoxane [(η5-C5Me4)(SiMe2NHNMe2)Ti]4O6 (7) with an adamantane-like cage structure. However, the reaction of 2 with H2O in the presence of HCl affords a dimeric complex [μ-(OSiMe2-η5-C5Me4)TiCl2]2 (8). Compounds 1−8 have been characterized by spectroscopic and analytical data. Molecular structures of 2, 3, 4, 5, 7, and 8 have been determined by single-crystal X-ray diffraction studies. Complexes 2−5 contain η1-hydrazido (2 and 4) and η2-hydrazido (3 and 5) groups depending on the electronic nature of the titanium center. Reversible interconversion between η1- and η2-hydrazido moieties has been observed upon addition of either NEt3 (4 → 5) or AlMe3 (5 → 4). Complexes 2−5 exhibit moderate catalytic activities for the polymerization of ethene in the presence of either methyaluminoxane (MAO) or AliBu3/Ph3C+B(C6F5)4 -.