Zirconium and Hafnium Hydrazinediido Half-Sandwich Complexes: Synthesis and Reactivity

The hydrazinediido complexes [Cp*M­(N<sub>xyl</sub>N)­(NNPh<sub>2</sub>)­(dmap)] (M = Zr, <b>3a</b>; M = Hf, <b>3b</b>; N<sub>xyl</sub>N = 2-(<i>N</i>-xylylamino)­pyrrolinate) have been synthesized, and their reactivity has been investigated. Both complexes were prepared from [Cp*M­(N<sub>xyl</sub>N)­Cl<sub>2</sub>] (<b>1a</b>,<b>b</b>) and [Cp*M­(N<sub>xyl</sub>N)­(NHNPh<sub>2</sub>)­Cl] (<b>2a</b>,<b>b</b>), respectively, as precursors. While <b>3a</b> was obtained by dehydrohalogenation of <b>2a</b> using LiHMDS in the presence of dmap, reaction of <b>2b</b> with LiHMDS initially afforded a mixture of [Cp*Hf­(N<sub>xyl</sub>N)­(NHNPh<sub>2</sub>)<sub>2</sub>] (<b>6</b>) and [Cp*Hf­(N<sub>xyl</sub>N)­(NNPh<sub>2</sub>)­LiHMDS] (<b>4</b>), which was thermolyzed subsequently in the presence of dmap to yield <b>3b</b>. [Cp*Zr­(N<sub>xyl</sub>N)­(NNPh<sub>2</sub>)­(dmap)] (<b>3a</b>) reacted with diisopropylcarbodiimide, giving the rearranged [2 + 2] cycloaddition product [Cp*Zr­(N<sub>Xyl</sub>N)­{κ<sup>2</sup>-N<sup>i</sup>PrC­(NNPh<sub>2</sub>)­N<sup>i</sup>Pr}] (<b>7</b>) and the six-membered zirconacycle [Cp*Zr­(N<sub>Xyl</sub>N)­{κ<sup>2</sup>-N­(NPh<sub>2</sub>)­C­(N<sup>i</sup>Pr)­N<sup>iPr</sup>C­(N<sup>i</sup>Pr)­N<sup>iPr</sup>}] (<b>8a</b>). With <i>N</i>-phenylbenzimine the cycloaddition product [Cp*Zr­(N<sub>Xyl</sub>N)­{κ<sup>2</sup>-N­(NPh<sub>2</sub>)­CHPhNPh}] (<b>9</b>) was isolated, and upon reaction with diphenylacetylene the seven-membered zirconacycle [Cp*Zr­(N<sub>Xyl</sub>N)­{κ<sup>2</sup>-N­(Ph)-<i>o</i>-phenylene-C­(Ph)C­(Ph)­NH}] (<b>10</b>) was obtained. Reaction of the previously synthesized compound [Zr­(N<sub>2</sub><sup>TBS</sup>N<sub>py</sub>)­(NNPh<sub>2</sub>)­py] (<b>11</b>) with <sup><i>i</i></sup>PrNCN<sup><i>i</i></sup>Pr and with PhCHNPh gave the four-membered zirconacycles [Zr­(N<sub>2</sub><sup>TBS</sup>N<sub>py</sub>)­{κ<sup>2</sup>-N­(NPh<sub>2</sub>)­C­(N<sup>i</sup>Pr)­N<sup>i</sup>Pr}] (<b>12</b>) and [Zr­(N<sub>2</sub><sup>TBS</sup>N<sub>py</sub>)­{κ<sup>2</sup>-N­(NPh<sub>2</sub>)­CHPhNPh}] (<b>13</b>), respectively.