Improved Synthesis and Structure of Solvated and Unsolvated Forms of Cyclooctatetraene–zirconium and –hafnium Dichloride

An improved synthesis for [M(η8-C8H8)Cl2(thf)] (M = Zr or Hf) and their unsolvated forms [M(η8-C8H8)Cl2] has been developed based on a ligand redistribution reaction between [M(η8-C8H8)(η4-C 8H8)] and [MCl4(thf)2] (thf = tetrahydrofuran). This reaction was proven to be valuable also in the case of substituted cyclooctatetraenes, as shown in the synthesis of [{Zr[η8-C8H6(SiMe3) 2]Cl}2(μ-Cl)2]. Crystallographic details: [Hf(η8-C8H8)Cl2(thf)], space group Cmca, a = 12.308(1), b = 12.005(1), c = 17.470(2) Å, α = β = γ = 90°, Z = 8, and R = 0.032 for 771 independent observed reflections; [{Zr[η8-C8H6(SiMe3) 2]Cl}2(μ-Cl)2], space group C2221, a = 10.498(1), b = 23.253(2), c = 15.830(1) Å, α = β = γ = 90°, Z = 4 and R = 0.048 for 3121 independent observed reflections.