Synthesis and Structures of Oxide -Centred Alkali Metal (K, Li)/Lanthanoid (Ln3 or 4) 3,5-Dimethylpyrazolate Cages - Herbert Schumann Revisited.

Reaction of lanthanoid tris(3,5-dimethylpyrazolate) compounds, [Ln(Me ₂ pz) ₃ (thf)] ₂ (Ln=La 1 a, Ce, Pr, Dy 1 b, Yb, Lu) with potassium or lithium bistrimethylsilylamide and with or without added 3,5-dimethylpyrazole, or of lanthanoid tris(bistrimethylsilyl)amide complexes with potassium bistrimethylsilylamide and 3,5-dimethylpyrazole have yielded a variety of oxide centred Ln ₃ or Ln ₄ /(K or Li) _1-3 multinuclear cages, namely, [La ₄ O(Me ₂ pz) ₁₁  K(thf) ₂ ] (2 a), [La ₄ O(Me ₂ pz) ₁₁ Li(Me ₂ pzH)]⋅0.5Hexane (2 b), [La ₄ O(Me ₂ pz) ₁₀ (Me ₂ pzH)] (2 c) (from heating 1 a in toluene), [Ce ₃ O(Me ₂ pz) ₉ K ₂ (dme) ₂ ] (3 a), [Ce ₃ O(Me ₂ pz) ₉ Li ₂ (thf) ₂ ]⋅0.5Hexane (3 b) and [Ce(Me ₂ pz) ₅ Li ₂ (thf) ₃ ] (3 c), which crystallized together, [Ce ₃ O(Me ₂ pz) ₁₀ K ₃ (thf) ₃ ] (3 d), [Pr ₃ O(Me ₂ pz) ₁₀ K ₃ (thf) ₃ ] (4), [Dy ₃ O(Me ₂ pz) ₉ K ₂ (thf) ₂ ]⋅THF (5), [Yb ₃ O(Me ₂ pz) ₉ K ₂ (thf) ₂ ]⋅THF (6), and [Lu ₃ O(Me ₂ pz) ₉ K ₂ (thf) ₂ ]⋅THF (7). Crystals of {[K ₈ (Me ₂ pz) ₈ (thf) ₂ ]⋅THF} _∞ (8) were also obtained from the preparation of 7. From reaction of [Ce(Me ₂ pz) ₃ (thf)] ₂ with potassium tert-butoxide in toluene, the cerium(IV) heterobimetallic polymer [Ce ₂ (Me ₂ pz) ₆ (OtBu) ₄ K ₂ ] _∞ (9) was isolated. In the Ln ₃ O and the Ln ₄ O cages, the Ln atoms have triangular and distorted tetrahedral arrangements about the central oxygen, respectively. The relationship of the alkali metals to the central oxygen varies considerably. Thus in 2 a, 2 b, there is no bonding, in 3 a, both K atoms interact weakly, in 3 b one of the two Li atom is bound, in 3 d, 4, one of three K atoms in bound, whilst in 5-7, both K atoms are bound. All metals are bound to the cages by a variety of pyrazolate binding modes, with up to five different exhibited in some structures, and a new coordination mode, μ ₄ -1κ(N):2κ(N'):η ⁵ :η ⁵ , was observed in two complexes. In the structure of 2 c, the coordinated Me ₂ pzH ligand binds to two metals through a single nitrogen, the first time this has been observed for a pyrazole donor. The complex 9 is polymeric with all metals bridged by butoxide donors as well as by Me ₂ pz groups.
(© 2024 Wiley-VCH GmbH.)