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Triamidoamine Chemistry of Zirconium

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posted on 01.10.1999, 00:00 by Colin Morton, Ian J. Munslow, Christopher J. Sanders, Nathaniel W. Alcock, Peter Scott
The reactions of H3(NN‘3) (NN‘3 = N(CH2CH2NSiButMe2)3) with [Zr(CH2Ph)4] and [Zr(NMe2)4] give the azazirconatranes [Zr(NN‘3)(CH2Ph)] and [Zr(NN‘3)(NMe2)], respectively. The reaction of [Li3(NN‘3)(THF)3] with [ZrCl4(THF)2] fails to yield [Zr(NN‘3)Cl] cleanly, but this compound is accessible by reaction of [Zr(NN‘3)(CH2Ph)] with BCl3 or of [Zr(NN‘3)(NMe2)] with SiMe3Cl. The molecular structures of [Zr(NN‘3)X] (X = CH2Ph, NMe2, Cl) show that the triamidoamine ligands adopt the usual 3-fold symmetric arrangement to give approximately trigonal-bipyramidal complexes. Attempted sublimation of [Zr(NN‘3)(CH2Ph)] or its treatment with H2 leads to clean conversion to the metallacyclic complex [Zr{N(CH2CH2NSiButMe2)2CH2CH2NSiButMeCH2}] via deprotonation of a silylmethyl group and elimination of toluene. The molecular structure of this complex contrasts with those above in that the tert-butyldimethylsilyl groups adopt an upright conformation as a consequence of the presence of the metallacyclic unit. The dihedral angles Nax−Zr−Neq−Si are in the range 173.8−177.2°. Exposure of the metallacycle to D2 gas leads to deuteration of all three Me2Si groups via sequential deuteriolysis/σ-bond metathesis. The less acidic tBuSi and backbone CH2 groups are unaffected.