Crystal data for bis(η⁵-tert-butylcyclopentadienyl)hafnium(IV) dihydride dimer, [(η⁵-t-BuC₅H₄)₂HfH(μ-H)]₂

The air-sensitive title hydride [Hf(C₉H₁₃)2H₂]₂ was prepared by hydrogenolysis of (t-BuCp)₂HfMe₂ [Couturier, Tainturier & Gautheron (1980). J. Organomet. Chem. 195, 291–306] and crystallized from a solution in heptane or toluene and hexane. The compound is triclinic with the following cell parameters: a = 7.22(3), b = 10.31(4), c = 12.47(6) Å, α = 80.4(4), β = 74.6(4)°, γ = 72.1(3)°, V = 847 ų, Z = 1, D_x = 1.67 Mg m^{− 3}. Powder diffraction data were obtained from Debye–Scherrer photographs. The extended version of the paper examines several examples where Zr or Hf hydrides are monomers or dimers and shows that this structure is very similar to the related [(MeCp)₂ZrH₂]₂ compound [Jones & Petersen (1981). Inorg. Chem. 20, 2889–2894]. This similarity and spectroscopic data show that the molecule probably has a center of symmetry situated between the two Hf atoms and the two bridging H atoms. The JCPDS Diffraction File No. for [Hf(C₉H₁₃)₂H₂]₂ is 33-1996.