Di-zirconium-nona-isopropoxide as a cyclopentadienyl replacement: synthesis and crystal structure of the di-zirconium-nona-isopropoxide lanthanide halides {[Zr2(OPri)9]Eu(µ-I)}2, {[Zr2(OPri)9]NdCl(µ-Cl)}2 and {[Zr2(OPri)9]Nd(µ-O2CBut)(µ-Cl)}2†

Abstract

Structural evidence has been obtained which suggests that the monoanionic polydentate moiety, Zr₂(OPrⁱ)₉^–, obtainable from KZr₂(OPrⁱ)₉ and Zr₂(OPrⁱ)₈(PrⁱOH)₂, can function as a replacement for cyclopentadienyl-containing ligand sets in established types of organolanthanide compounds. The Zr₂(OPrⁱ)₉^– unit has been found to replace the ligand set [(C₅Me₅)(thf)₂]^– (thf = tetrahydrofuran) in [(C₅Me₅)(thf)₂Sm(µ-I)]₂ and the ligand set [(C₅H₅)₂]^2– in [(C₅H₅)₂Nd(thf)(µ-Cl)]₂. The complex KZr₂(OPrⁱ)₉ reacts with LnI₂(thf)₂ (Ln = Eu or Sm) in toluene to form the isostructural, isomorphous complexes {[Zr₂(OPrⁱ)₉]Ln(µ-I)}₂, which crystallize from toluene (1: {[Zr₂(OPrⁱ)₉Eu(µ-I)}₂, P2₁/n, a = 12.082(2), b = 19.309(3), c = 17.294(3) Å, β = 92.805(11)°, U = 4029.4(12) ų and D_c = 1.637 g cm^–3 for Z = 2; 2: {[Zr₂(OPrⁱ)₉]Sm(µ-I)}₂, P2₁/n, a = 12.071(2), b = 19.273(3), c = 17.279(2) Å, β = 92.679(12)°, U = 4015.4(8) ų and D_c = 1.640 Mg m^–3 for Z = 2). The face-sharing bioctahedral Zr₂(OPrⁱ)₉^– unit uses two of its central isopropoxide ligands and one additional isopropoxide on each zirconium to attach to the lanthanide metal, which has a distorted octahedral co-ordination environment completed by two bridging iodide ligands. The complex Zr₂(OPrⁱ)₈(PrⁱOH)₂ reacts with NdCl₃ in thf to form {[Zr₂(OPrⁱ)₉]NdCl(µ-Cl)}₂ 3, which crystallizes from toluene [C2/c, a = 25.283(5), b = 12.505(3), c = 18.162(2) Å, β = 119.802(9)°, U = 8553.6(22) ų and D_c = 1.515 Mg m^–3 for Z = 4]. In 3 the Zr₂(OPrⁱ)₉^– unit again functions as a tetradentate ligand as in 1 and 2. Two bridging and one terminal chloride complete the pentagonal bipyramidal environment of Nd. A derivative of 3 in which the terminal chlorides are replaced by bridging pivalate groups is obtained by reacting NdCl₃ with KO₂CBu^t and Zr₂(OPrⁱ)₈(PrⁱOH) in thf to form {[Zr₂(OPrⁱ)₉]Nd(µ-O₂CBu^t)(µ-Cl)}₂ 4, which crystallizes from toluene [P, a = 12.267(3), b = 14.217(4), c = 14.700(3) Å, α = 88.08(2), β = 71.98(2), γ = 78.37(2)°, U = 2386.7(10) ų and D_c = 1.485 Mg m^–3 for Z = 1].