Migratory Insertion Reactions in Asymmetrical Guanidinate-Supported Zirconium Complexes

The new diguanidinate-supported dibenzylzirconium complexes [Zr­{κ²<i>N</i>,<i>N</i>′-(N-<i>i</i>-Pr)­(NAr)­CNH­(<i>i</i>-Pr)}₂(CH₂Ph)₂] (Ar = 4-<i>t</i>-BuC₆H₄ (<b>1</b>), 4-BrC₆H₄ (<b>2</b>)) and [Zr­{κ²<i>N</i>,<i>N</i>′-(NEt)­(N-<i>t</i>-Bu)­CNMe₂}₂(CH₂Ph)₂] (<b>3</b>) have been prepared. Complexes <b>1</b> and <b>2</b> were synthesized by protonolysis of [Zr­(CH₂Ph)₄] with the guanidine derivatives and complex <b>3</b> by treating [Zr­{κ²<i>N</i>,<i>N</i>′-(NEt)­(N-<i>t</i>-Bu)­CNMe₂}₂Cl₂] (<b>4</b>) with MgCl­(CH₂Ph). The treatment of <b>1</b>–<b>3</b> with 2,6-dimethylphenyl isocyanide (XyNC) results in migratory insertion and formation of the terminal imido species [Zr­{κ²<i>N</i>,<i>N</i>′-(N-<i>i</i>-Pr)­(N­(Ar))­CNH­(<i>i</i>-Pr)}₂{N­(2,6-Me₂C₆H₃)}] (Ar = 4-<i>t</i>-BuC₆H₄ (<b>7</b>), 4-BrC₆H₄ (<b>8</b>)) with <b>1</b> and <b>2</b>, respectively, whereas the analogous reaction with <b>3</b> leads to the enediamido complex [Zr­{κ²<i>N</i>,<i>N</i>′-(NEt)­(N-<i>t</i>Bu)­CNMe₂)}₂{N­(2,6-Me₂C₆H₃)­(CH₂Ph)­CC­(CH₂Ph)­N­(2,6-Me₂C₆H₃)}] (<b>9</b>). All the intermediate iminoacyl complexes have been characterized, and the molecular structures of <b>2</b>, <b>4</b>, and <b>9</b> have been determined by single-crystal X-ray diffraction