Synthesis of L2Ni(ORF)2 (RF = C(CF3)3) Complexes and Their Reactivity in Ethylene Oligomerization

Unravelling the Role of the Pentafluoroorthotellurate Group as a Ligand in Nickel Chemistry

The pentafluoroorthotellurate group (teflate, OTeF₅ ) is able to form species, for which only the fluoride analogues are known. Despite nickel fluorides being widely investigated, nickel teflates have remained elusive for decades. By reaction of [NiCl₄ ]^2- and neat ClOTeF₅ , we have synthesized the homoleptic [Ni(OTeF₅ )₄ ]^2- anion, which presents a distorted tetrahedral structure, unlike the polymeric [NiF₄ ]^2- . This high-spin complex has allowed the study of the electronic properties of the teflate group, which can be classified as a weak/medium-field ligand, and therefore behaves as the fluoride analogue also in ligand-field terms. The teflate ligands in [NEt₄ ]₂ [Ni(OTeF₅ )₄ ] are easily substituted, as shown by the formation of [Ni(NCMe)₆ ][OTeF₅ ]₂ by dissolving it in acetonitrile. Nevertheless, careful reactions with other conventional ligands have enabled the crystallization of nickel teflate complexes with different coordination geometries, i.e. [NEt₄ ]₂ [trans-Ni(OEt₂ )₂ (OTeF₅ )₄ ] or [NEt₄ ][Ni(bpyMe₂ )(OTeF₅ )₃ ].