Mononuclear Amido and Binuclear Imido Zirconium Complexes Supported by Dibenzotetraaza[14]annulene Ligands. X-ray Structure of [(Me₄taa)Zr(μ-NR)₂Zr(NHR)₂] (R = Bu^t or 2,6-C₆H₃Me₂)

Reaction of 2 equiv of Li[NH-2,6-C₆H₃R₂] with [(Me₄taa)ZrCl₂] (Me₄taaH₂ = tetramethyldibenzotetraaza[14]annulene) gives the bis(amido) derivatives [(Me₄taa)Zr(NH-2,6-C₆H₃R₂)₂] [R = Prⁱ (1) and Me (2)]. Addition of Me₄taaH₂ to [Zr(N-2,6-C₆H₃Prⁱ₂)(NH-2,6-C₆H₃Prⁱ₂)₂(py)₂] also affords 1. The reaction of 2 equiv of aryl or alkyl amines H₂NR with the bis(alkyl) complex [(Me₄taa)Zr(CH₂SiMe₃)₂] is the most versatile method for preparing [(Me₄taa)Zr(NHR)₂] (R = 2,6-C₆H₃Prⁱ₂, 2,6-C₆H₃Me₂, Ph, or Bu^t). Reaction of 1 equiv of Me₄taaH₂ with the binuclear complexes [(Bu^tNH)₂Zr(μ-NBu^t)₂Zr(NHBu^t)₂] or [(py)(HN-2,6-C₆H₃Me₂)₂Zr(μ-N-2,6-C₆H₃Me₂)₂Zr(NH-2,6-C₆H₃Me₂)₂(py)] gives the asymmetrically substituted derivatives [(Me₄taa)Zr(μ-NR)₂Zr(NHR)₂] [R = Bu^t (6) or 2,6-C₆H₃Me₂ (8)], which have been crystallographically characterized.