Terminal Zirconium Imides Prepared by Reductive C−N Bond Cleavage

Toluene reflux of ZrCl 4 with Li(Nacnac) (Nacnac - = [Ar]NC( t Bu)CHC( t Bu)N[Ar], Ar = 2,6-[CH(CH 3 ) 2 ] 2 C 6 H 3 ) provides the complex (Nacnac)ZrCl 3 in 75% yield. Cl - substitution for OTf - is readily achieved with 3 equiv of AgOTf to yield 77% of the complex (Nacnac)Zr(OTf) 2 (η 2 -OTf). The coordination mode of the three triflato groups was determined by a combination of single-crystal X-ray analysis and 19 F COSY experiments. Addition of 2 equiv of LiCH 2 XMe 3 (X = C, Si) to (Nacnac)ZrCl 4 in Et 2 O affords the bis(alkyl) systems (Nacnac)Zr(CH 2 XMe 3 ) 2 Cl in good yield (X = C, 86%; X = Si, 91%). In contrast, reaction of (Nacnac)Zr(OTf) 2 (η 2 -OTf) with 2 equiv of LiCH 2 CMe 3 leads instead to formation of the terminal zirconium−imido complex [(Nac t Bu)Zr NAr(μ 2 -OTf)] 2 (Nac t Bu - = [2,6-(CHMe 2 ) 2 C 6 H 3 ]NC( t Bu)CHC( t Bu)). Likewise, reduction of (Nacnac)ZrCl 3 with 2 equiv of KC 8 in THF also affords a terminal zirconium−imido species, (Nac t Bu)Zr NAr(Cl)(THF). The zirconium−imido compounds described herein result from reductive cleavage of the C−N bond of the imine functionality contained in the Nacnac - ligand. The complexes (Nacnac)ZrCl 3, (Nacnac)Zr(OTf) 2 (η 2 -OTf), (Nacnac)Zr(CH 2 XMe 3 ) 2 Cl, [(Nac t Bu)Zr NAr(μ 2 -OTf)] 2, and (Nac t Bu)Zr NAr(Cl)(THF) have been fully characterized, and a single-crystal X-ray diffraction analysis is reported for each.