Migratory Insertion Reactions in Asymmetrical Guanidinate-Supported Zirconium Complexes

The new diguanidinate-supported dibenzylzirconium complexes [Zr­{κ2N,N′-(N-i-Pr)­(NAr)­CNH­(i-Pr)}2(CH2Ph)2] (Ar = 4-t-BuC6H4 (1), 4-BrC6H4 (2)) and [Zr­{κ2N,N′-(NEt)­(N-t-Bu)­CNMe2}2(CH2Ph)2] (3) have been prepared. Complexes 1 and 2 were synthesized by protonolysis of [Zr­(CH2Ph)4] with the guanidine derivatives and complex 3 by treating [Zr­{κ2N,N′-(NEt)­(N-t-Bu)­CNMe2}2Cl2] (4) with MgCl­(CH2Ph). The treatment of 1–3 with 2,6-dimethylphenyl isocyanide (XyNC) results in migratory insertion and formation of the terminal imido species [Zr­{κ2N,N′-(N-i-Pr)­(N­(Ar))­CNH­(i-Pr)}2{N­(2,6-Me2C6H3)}] (Ar = 4-t-BuC6H4 (7), 4-BrC6H4 (8)) with 1 and 2, respectively, whereas the analogous reaction with 3 leads to the enediamido complex [Zr­{κ2N,N′-(NEt)­(N-tBu)­CNMe2)}2{N­(2,6-Me2C6H3)­(CH2Ph)­CC­(CH2Ph)­N­(2,6-Me2C6H3)}] (9). All the intermediate iminoacyl complexes have been characterized, and the molecular structures of 2, 4, and 9 have been determined by single-crystal X-ray diffraction.