Bis(cyclooctatetraene) derivatives of zirconium(IV) and hafnium(IV): syntheses and Lewis base adducts. Crystal structures of [Zr(η8-C8H8)(η4-C8H8)], [Hf{η8-C8H6(SiMe3)2}{η4-C8H6(SiMe3)2}], [Zr(η8-C8H8)(η4-C8H8)(NH3)] and [Zr(η8-C8H8)(η4-C8H8)(CNBut)]
Abstract
The syntheses of [M(η8-C8H8)(η4-C8H8)](M = Zr, 2 or Hf, 3) and [M{η8-C8H6(SiMe3)2}{η4-C8H6(SiMe3)2}](M = Zr, 4 or Hf, 5) are reported. The η8 and η4 bonding modes for C8H8 were established in the solid state by X-ray analyses, while in solution a single C8H8 environment was observed by 1H NMR spectroscopy even at low temperature in accord with fluxional behaviour for these compounds. Complexes 2–5 behave as Lewis acids toward tetrahydrofuran, NH3 and ButNC and the adducts [Zr(η8-C8H8)(η4-C8H8)(NH3)]6 and [M(η8-C8H8)(η4-C8H8)(CNBut)](M = Zr, 7 or Hf, 8) have been isolated and characterized by X-ray analysis. Crystallographic details: 2, monoclinic, space group P21/c, a= 13.754(1), b= 7.798(1), c= 12.753(1)Å, β= 114.02(1)°, Z= 4 and R= 0.037 for 1267 independent observed reflections; 5, orthorhombic, space group Pca21, a= 14.418(1), b= 11.285(1), c= 18.898(1)Å, Z= 4 and R= 0.036 for 2239 independent observed reflections; 6, orthorhombic, space group P212121, a= 9.815(1), b= 14.129(2), c= 9.561(1)Å, Z= 4 and R= 0.022 for 1556 independent observed reflections; 7, triclinic, space group P, a= 11.172(1), b= 13.469(1), c= 14.303(1)Å, α= 62.80(1), β= 78.01(1), γ= 77.26(1)°, Z= 4 and R= 0.028 for 2994 independent observed reflections.