Terminal zirconium imides prepared by reductive C-N bond cleavage

Toluene reflux of ZrCl4 with Li(Nacnac) (Nacnac(-) = [Ar]NC(tBu)CHC(tBu)N[Ar], Ar = 2,6-[CH(CH3)(2)](2)C6H3) provides the complex (Nacnac)ZrCl3 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)(eta(2)-OTf). The coordination mode of the three triflato groups was determined by a combination of single-crystal X-ray analysis and F-19 COSY experiments. Addition of 2 equiv of LiCH2XMe3 (X = C, Si) to (Nacnac)ZrCl4 in Et2O affords the bis(alkyl) systems (Nacnac)Zr(CH2XMe3)(2)Cl in good yield (X = C, 86%; X = Si, 91%). In contrast, reaction of (Nacnac)Zr(OTf)(2)(eta(2)-OTf) with 2 equiv of LiCH2CMe3 leads instead to formation of the terminal zirconium-imido complex [(NactBu)Zr=NAr(mu(2)-OTf)](2) (NactBu(-) = [2,6-(CHMe2)(2)C6H3]NC(tBu)CHC(tBu)). Likewise, reduction of (Nacnac)ZrCl3 with 2 equiv of KC8 in THF also affords a terminal zirconium-imido species, (NactBu)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)ZrCl3, (Nacnac)Zr(OTf)(2)(eta(2)-OTf), (Nacnac)Zr(CH2XMe3)(2)Cl, [(NactBu)Zr=NAr(mu(2)-OTf)](2), and (NactBu)Zr=NAr(Cl)(THF) have been fully characterized, and a single-crystal X-ray diffraction analysis is reported for each.