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

The hydrazinediido complexes [Cp*M­(N_xylN)­(NNPh₂)­(dmap)] (M = Zr, <b>3a</b>; M = Hf, <b>3b</b>; N_xylN = 2-(<i>N</i>-xylylamino)­pyrrolinate) have been synthesized, and their reactivity has been investigated. Both complexes were prepared from [Cp*M­(N_xylN)­Cl₂] (<b>1a</b>,<b>b</b>) and [Cp*M­(N_xylN)­(NHNPh₂)­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_xylN)­(NHNPh₂)₂] (<b>6</b>) and [Cp*Hf­(N_xylN)­(NNPh₂)­LiHMDS] (<b>4</b>), which was thermolyzed subsequently in the presence of dmap to yield <b>3b</b>. [Cp*Zr­(N_xylN)­(NNPh₂)­(dmap)] (<b>3a</b>) reacted with diisopropylcarbodiimide, giving the rearranged [2 + 2] cycloaddition product [Cp*Zr­(N_XylN)­{κ²-NⁱPrC­(NNPh₂)­NⁱPr}] (<b>7</b>) and the six-membered zirconacycle [Cp*Zr­(N_XylN)­{κ²-N­(NPh₂)­C­(NⁱPr)­N^iPrC­(NⁱPr)­N^iPr}] (<b>8a</b>). With <i>N</i>-phenylbenzimine the cycloaddition product [Cp*Zr­(N_XylN)­{κ²-N­(NPh₂)­CHPhNPh}] (<b>9</b>) was isolated, and upon reaction with diphenylacetylene the seven-membered zirconacycle [Cp*Zr­(N_XylN)­{κ²-N­(Ph)-<i>o</i>-phenylene-C­(Ph)C­(Ph)­NH}] (<b>10</b>) was obtained. Reaction of the previously synthesized compound [Zr­(N₂^TBSN_py)­(NNPh₂)­py] (<b>11</b>) with ^<i>i</i>PrNCN^<i>i</i>Pr and with PhCHNPh gave the four-membered zirconacycles [Zr­(N₂^TBSN_py)­{κ²-N­(NPh₂)­C­(NⁱPr)­NⁱPr}] (<b>12</b>) and [Zr­(N₂^TBSN_py)­{κ²-N­(NPh₂)­CHPhNPh}] (<b>13</b>), respectively