220489-77-0Relevant academic research and scientific papers
Formation and structures of [1,2-bis(N-tert- butylcarbamoyl)cyclopentadienyl]zirconium complexes - Coordination chemistry of a 'fulvenologous' malonic amide anion ligand system
Klass, Katrin,Duda, Lothar,Kleigrewe, Nina,Erker, Gerhard,Froehlich, Roland,Wegelius, Elina
, p. 11 - 19 (1999)
Treatment of sodium cyclopentadienide with two molar equivalents of tert-butyl isocyanate yields sodium 1,2-bis(N-tert- butylcarbamoyl)cyclopentadienide (6). The [C5H3(1,2-CONHCMe3)2]Na reagent 6 adds to Cp2Zr(CH3)Cl (8) to yield Cp2Zr(CH3)[C5H3(CONHCMe3)2] (9). In 9 the C5H3(CONHCMe3)2 ligand is bonded to zirconium through one of its carboxamido-oxygen atoms (κO-coordination). Treatment of 6 with CpZrCl3(THF)2 yields CpZrCl2[C5H3(CONHCMe3)2](THF) 11. In 11 the 1,2- bis(N-tert-butylcarbamoyl)cyclopentadienide moiety serves as a C(s)-symmetric chelate ligand, binding to zirconium through both carbamoyl oxygens (κ2O,O'-coordination). The same seven-membered metallacyclic structural type is found in the reaction products of 6 with ZrCl4(THF)2 in 1:1 and 2:1 molar ratios. The former yields the distorted octahedral complex ZrCl3[C5H3(CONHCMe3)2](THF) (12), the latter gives the chiral octahedral system ZrCl2[C5H3(CONHCMe3)2]2 (13). In solution, complex 13 undergoes a thermally induced enantiomerization process (Λ ? Δ interconversion), for which a Gibbs activation energy of ΔG(+/+)(enant) = 14.0 ± 0.3 kcal mol- 1 was determined by dynamic 1H-NMR spectroscopy. The κ2O,O'-coordination of the [C5H3(1,2-CONHCMe3]- ligand in the complexes 11, 12, and 13 was secured by X-ray crystal structure analyses.
