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Terminal Zirconium Imides Prepared by Reductive C−N Bond Cleavage

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posted on 20.12.2004, 00:00 authored by Falguni Basuli, Uriah J. Kilgore, Douglas Brown, John C. Huffman, Daniel J. Mindiola
Toluene reflux of ZrCl4 with Li(Nacnac) (Nacnac- = [Ar]NC(tBu)CHC(tBu)N[Ar], Ar = 2,6-[CH(CH3)2]2C6H3) 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)22-OTf). The coordination mode of the three triflato groups was determined by a combination of single-crystal X-ray analysis and 19F COSY experiments. Addition of 2 equiv of LiCH2XMe3 (X = C, Si) to (Nacnac)ZrCl4 in Et2O affords the bis(alkyl) systems (Nacnac)Zr(CH2XMe3)2Cl in good yield (X = C, 86%; X = Si, 91%). In contrast, reaction of (Nacnac)Zr(OTf)22-OTf) with 2 equiv of LiCH2CMe3 leads instead to formation of the terminal zirconium−imido complex [(NactBu)ZrNAr(μ2-OTf)]2 (NactBu- = [2,6-(CHMe2)2C6H3]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)22-OTf), (Nacnac)Zr(CH2XMe3)2Cl, [(NactBu)ZrNAr(μ2-OTf)]2, and (NactBu)ZrNAr(Cl)(THF) have been fully characterized, and a single-crystal X-ray diffraction analysis is reported for each.