Fe(OTeF5)3, Darstellung, Struktur und Reaktivit�t

Further Perspectives on the Teflate versus Fluoride Analogy: The Case of a Co(II) Pentafluoroorthotellurate Complex

The pentafluoroorthotellurate group (teflate, OTeF5) is considered as a bulky analogue of fluoride, yet its coordination behavior in transition metal complexes is not fully understood. By reaction of [CoCl4]2- and neat ClOTeF5, we synthesized the first cobalt teflate complex, [Co(OTeF5)4]2-, which exhibits moisture-resistant Co-OTeF5 bonds. Through a combined experimental and theoretical (DFT and NEVPT2) study, the properties and electronic structure of this species have been investigated. It exhibits a distorted tetrahedral structure around the cobalt center and can be described as a d7 system with a quartet (S = 3/2) ground state. A comparative bonding analysis of the (pseudo)tetrahedral [CoX4]2- anions (X = OTeF5, F, Cl) revealed that the strength of the Co-X interaction is similar in the three cases, being the strongest in [Co(OTeF5)4]2-. In addition, an analysis of the charge of the Co center reinforced the similar electron-withdrawing properties of the teflate and fluoride ligands. Therefore, the [Co(OTeF5)4]2- anion constitutes an analogue of the polymeric [CoF4]2- in terms of electronic properties, but with a monomeric structure.

Gold Teflates Revisited: From the Lewis Superacid [Au(OTeF5 )3 ] to the Anion [Au(OTeF5 )4 ]. Chemistry 2023;29:e202203634. [PMID: 36598847 DOI: 10.1002/chem.202203634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

A new synthetic access to the Lewis acid [Au(OTeF₅ )₃ ] and the preparation of the related, unprecedented anion [Au(OTeF₅ )₄ ]^- with inorganic or organic cations starting from commercially available and easy-to-handle gold chlorides are presented. In this first extensive study of the Lewis acidity of a transition-metal teflate complex by using different experimental and quantum chemical methods, [Au(OTeF₅ )₃ ] was classified as a Lewis superacid. The solid-state structure of the triphenylphosphine oxide adduct [Au(OPPh₃ )(OTeF₅ )₃ ] was determined, representing the first structural characterization of an adduct of this highly reactive [Au(OTeF₅ )₃ ]. Therein, the coordination environment around the gold center slightly deviates from the typical square planar geometry. The [Au(OTeF₅ )₄ ]^- anion shows a similar coordination motif.

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 ].

Lewis Superacidic Catecholato Phosphonium Ions: Phosphorus-Ligand Cooperative C-H Bond Activation

A series of catecholato phosphonium ions, including the first stable bis(catecholato)-substituted derivatives, are isolated and fully characterized. The cations rank among the most potent literature-known Lewis acids on the Gutmann-Beckett and ion affinity scales. In contrast to halogenated or multiply charged phosphorus cations, Lewis superacidity is imparted by structural constraints, as disclosed by energy decomposition analysis. The modular access provides a tunable scaffold while maintaining extreme affinity, demonstrated by the synthesis of a chiral Lewis superacid. The combination of electrophilic phosphorus and basic oxygen substituents leverages new reactivity modes by phosphorus-ligand cooperativity. With this, a phosphorus-mediated C-H bond activation is accomplished.

The nature of the chemical bond in linear three-body systems: from i3- to mixed chalcogen/halogen and trichalcogen moieties

The 3 centre-4 electrons (3c-4e) and the donor/acceptor or charge-transfer models for the description of the chemical bond in linear three-body systems, such as I(3) (-) and related electron-rich (22 shell electrons) systems, are comparatively discussed on the grounds of structural data from a search of the Cambridge Structural Database (CSD). Both models account for a total bond order of 1 in these systems, and while the former fits better symmetric systems, the latter describes better strongly asymmetric situations. The 3c-4e MO scheme shows that any linear system formed by three aligned closed-shell species (24 shell electrons overall) has reason to exist provided that two electrons are removed from it to afford a 22 shell electrons three-body system: all combinations of three closed-shell halides and/or chalcogenides are considered here. A survey of the literature shows that most of these three-body systems exist. With some exceptions, their structural features vary continuously from the symmetric situation showing two equal bonds to very asymmetric situations in which one bond approaches to the value corresponding to a single bond and the second one to the sum of the van der Waals radii of the involved atoms. This indicates that the potential energy surface of these three-body systems is fairly flat, and that the chemical surrounding of the chalcogen/halogen atoms can play an important role in freezing different structural situations; this is well documented for the I(3) (-) anion. The existence of correlations between the two bond distances and more importantly the linearity observed for all these systems, independently on the degree of their asymmetry, support the state of hypervalency of the central atom.

Synthesis, structural characterization, and computational study of the strong oxidant salt [XeOTeF5][Sb(OTeF5)6].SO2ClF

The strong oxidant salt [XeOTeF(5)][Sb(OTeF(5))(6)].SO(2)ClF has been synthesized by reaction of stoichiometric amounts of Xe(OTeF(5))(2) and Sb(OTeF(5))(3) in SO(2)ClF solution at -78 degrees C and characterized in SO(2)ClF solution by low-temperature (17)O, (19)F, (121)Sb, (125)Te, and (129)Xe NMR spectroscopy, showing the Xe...O donor-acceptor bond XeOTeF(5)(+).SO(2)ClF adduct-cation to be labile at temperatures as low as -80 degrees C. The salt crystallizes from SO(2)ClF as [XeOTeF(5)][Sb(OTeF(5))(6)].SO(2)ClF, and the low-temperature crystal structure was obtained: triclinic, P, a = 9.7665(5) A, b = 9.9799(4) A, c = 18.5088(7) A, alpha = 89.293(2) degrees , beta = 82.726(2) degrees , gamma = 87.433(3) degrees , V = 1787.67(13) A(3), Z = 2, and R(1) = 0.0.0451 at -173 degrees C. Unlike MF(6)(-) in [XeF][MF(6)] (e.g., M = As, Sb, Bi) and [XeOTeF(5)][AsF(6)], the Sb(OTeF(5))(6)(-) anion is significantly less basic and does not interact with the coordinately unsaturated xenon(II) cation. Rather, the XeOTeF(5)(+) cation and weak Lewis base, SO(2)ClF, interact by coordination of an oxygen atom of SO(2)ClF to xenon [Xe...O, 2.471(5) A]. The XeOTeF(5)(+).SO(2)ClF adduct-cation has also been studied by low-temperature Raman spectroscopy, providing frequencies that have been assigned to adducted SO(2)ClF. The solid-state Raman spectra of XeOTeF(5)(+).SO(2)ClF and Sb(OTeF(5))(6)(-) have been assigned with the aid of electronic structure calculations. In addition to optimized geometries and vibrational frequencies, theoretical data, including gas-phase donor-acceptor bond energies, natural bond orbital (NBO) analyses, and topological analyses based on electron localization functions (ELF), provide descriptions of the bonding in XeOTeF(5)(+).SO(2)ClF and related systems. The quantum mechanical calculations provided consistent trends for the relative strengths of the Xe...O donor-acceptor bond in XeOTeF(5)(+).SO(2)ClF and ion-pair bonds in [XeL][MF(6)] (L = F, OTeF(5); M = As, Sb), with the Xe...O bond of XeOTeF(5)(+).SO(2)ClF being the weakest in the series.

Synthesis and Characterization by (19)F and (125)Te NMR and Raman Spectroscopy of cis-ReO(2)(OTeF(5))(3) and cis-ReO(2)(OTeF(5))(4)(-), and X-ray Crystal Structure of [N(CH(3))(4)(+)][cis-ReO(2)(OTeF(5))(4)(-)]

The pentafluorooxotellurate compound ReO(2)(OTeF(5))(3) has been synthesized from the reaction of ReO(2)F(3) with B(OTeF(5))(3) and structurally characterized in solution by (19)F and (125)Te NMR spectroscopy and in the solid state by Raman spectroscopy. The NMR and vibrational spectroscopic findings are consistent with a trigonal bipyramidal arrangement in which the oxygen atoms and an OTeF(5) group occupy the equatorial plane. The (19)F and (125)Te NMR spectra show that the axial and equatorial OTeF(5) groups of ReO(2)(OTeF(5))(3) are fluxional and are consistent with intramolecular exchange by means of a pseudorotation. The Lewis acid behavior of ReO(2)(OTeF(5))(3) is demonstrated by reaction with OTeF(5)(-). The resulting cis-ReO(2)(OTeF(5))(4)(-) anion was characterized as the tetramethylammonium salt in solution by (19)F and (125)Te NMR spectroscopy and in the solid state by Raman spectroscopy and X-ray crystallography. The compound crystallizes in the triclinic system, space group P&onemacr;, with a = 13.175(7) Å, b = 13.811(5) Å, c = 15.38(1) Å, alpha = 72.36(5)(o), beta = 68.17(5)(o), gamma = 84.05(4)(o), V = 2476(2) Å(3), D(calc) = 3.345 g cm(-)(3), Z = 4, R = 0.0547. The coordination sphere about Re(VII) in cis-ReO(2)(OTeF(5))(4)(-) is a pseudooctahedron in which the Re-O double bond oxygens are cis to one another.