Noble Gas Fluorides Research Articles

Bartlett's discovery of noble gas fluorides, a milestone in chemical history

In 1962, Neil Bartlett published a terse note in Proc. Chem. Soc. eradicating the long held dogma that noble gases are inert and cannot form stable compounds. This historical discovery has revolutionized our views on chemistry and has given rise to thousands of papers on noble gas chemistry. The fact that his proposed reaction product "Xe(+)[PtF6](-)" has eluded experimental detection for more than half a century and actually was a mixture of XeF(+) and Xe2F3(+) salts does not diminish the enormous impact of his discovery. A plausible explanation for the failures to observe "Xe(+)[PtF6](-)" experimentally is presented.

Structure of simple and complex noble gas fluorides

The structural parameters of simple and complex fluorides of noble gases in different aggregate states have been analyzed. The data on their molecular and crystal structure are reported. The structural features of simple, coordination, polymer, and clathrate-like compounds of krypton and xenon fluorides are considered

New class of coordination compounds with noble gas fluorides as ligands to metal ions

A new class of coordination compounds of the type [M n+ (L) p ](AF 6 −) n and [M n+ (L) r ](BF 4 −) n , where M is Mg, Ca, Sr, Ba, Cd, Pb, lanthanides, A is P, As, Sb, Bi and L is XeF 2, XeF 4, XeF 6, KrF 2, was studied. A review of all known coordination compounds with L is XeF 2 is given: (a) synthetic routes for the preparation of these compounds; (b) analysis of their crystal structures (molecular, dimer, chain, double chain, layer, strongly interconnected double layers and three-dimensional network); (c) the influence of the ligand XeF 2 (small formula volume, linear, semi-ionic, charge of −0.5 e on each F ligand); (d) the influence of the central metal ion; (e) the influence of the anions: AF 6 − and BF 4 − (the formula volume, Lewis basicity). On the basis of all properties of the metal ions, ligand and anions the obtained variety of the structures is analyzed.

Well-tempered model core potentials for groups 17 and 18

New family of model core potentials (MCPs) based on the well-tempered basis set expansions was introduced for the elements of groups 17 and 18. Both small- and large-core potentials were developed. The new potentials were tested in RHF calculations for the diatomic halogen and polyatomic interhalogen compounds, and for noble-gas fluorides. For the small-core potentials, the agreement with the results of all-electron calculations using the well-tempered basis sets is excellent.

Paradigms and Paradoxes: Exothermicity of Some Reactions Involving the Noble Gas Fluorides and Oxides

It has long been known that the oxidizing/fluorinating power of noble gas fluorides increases in the order XeF2 < XeF4 < XeF6 < KrF2. While this does not initially appear surprising, a more careful investigation based on enthalpy and kechanistic considerations show some unexpected features. Reconciliation of these features also provides some understanding of the explosive nature of the sole isolable, noble gas oxides, XeO3 and XeO4.

ChemInform Abstract: Vibrational Spectra and Structural Features of Noble Gas Fluorides in Cryogenic and Nonaqueous Solutions

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Vibrational spectra and structural features of noble gas fluorides in cryogenic and nonaqueous solutions

Data on the vibrational spectra of noble gas fluorides in the gas phase and in cryogenic and nonaqueous solutions are considered in detail. Based on analysis of the IR spectra of xenon fluorides dissolved in liquid Kr and Xe, it is concluded that the XeF6 molecule possesses the geometry of a distorted octahedron withC 3v symmetry. The contours of spectral lines of totally symmetric stretching modes in the Raman spectra of noble gas fluorides in nonaqueous solutions are considered; the mechanisms of formation contours of these lines, the dynamic parameters of XeF n (n=2, 4, 6) and KrF2, and the characteristic times of intramolecular rearrangements in the nonrigid XeF6 molecule are analyzed. It is concluded that in the XeF2-HF and XeF6-HF systems, a number of associates and ionic clusters are formed due to the donor-acceptor interaction of the Lewis bases and acids.

New synthetic routes to binary and complex fluorides

Some new examples of the use of noble gas fluorides (e.g. XeF 2, XeF 6 and KrF 2) as reagents in preparative inorganic chemistry will be shown. XeF 2 is used as an oxidizing and fluorinating agent in the reactions with ammonium fluorometalates yielding ammonium fluorometalates in higher oxidation states. When oxides react with XeF 2, different products ( e.g., xenon(II) fluorometalates, oxide fluorides and binary fluorides) are obtained, depending on the reaction conditions. Xenon(VI) fluorometalates are synthesized using XeF 6 and different starting materials (e.g. oxides, hydrazinium or ammonium fluorometalates). In the cases when we are looking for complexes with the metal in a higher oxidation state, the combination KrF 2 and XeF 6 has to be used [K. Lutar, A. Jesih and B. Žemva, Rev. Chim. Miner., 23 (1986) 565]. The best synthetic approach for the preparation of binary fluorides, especially thermally unstable ones, is their precipitation from anhydrous hydrogen fluoride (AHF) solutions of their XeF 5 + salts by addition of fluoroacids [B. Žemva, K. Lutar, A. Jesih, W.J. Casteel, Jr and N. Bartlett, J. Chem. Soc., Chem. Commun. (1989) 346]. Those binary fluorides, which are weak fluoroacids, can be obtained simply by solvolysis of their salts with AHF. Growing of crystals in the supercritical fluids will be discussed. Vibrational spectra of new isolated compounds and some of their structures will be discussed.

Reactions between chromium fluorides and noble gas fluorides

In the system chromium(V) fluoride — xenon(II) fluoride besides of already known XeF 2·2CrF 4 [1] also a new blue xenon(II) fluorochromate(IV) was isolated by the reaction: CrF 5 + nXeF 2 → XeF 2·CrF 4 + 1 2 XeF 4 + (n−1.5)XeF 2. This compound was obtained also by the reaction: CrF 4 + nXeF 2 → XeF 2·CrF 4 + (n−1)XeF 2. Xenon difluoride is not able to oxidize chromium above 3+ oxidation state. Brick red XeF 6·CrF 4 [2] was isolated in the system chromium fluorides (CrF x with x being 2, 3, 4, 5) — xenon hexafluoride. It is observed that CrF 5 is reduced to 4+ oxidation state even in oxidative environmnet of xenon hexafluoride. Although considered as a relatively strong Lewis acid, CrF 5 is not strong enough to form its XeF 5 + salt. From vibrational spectra it could be concluded that XeF 2·CrF 4 is XeF + salt and XeF 6·CrF 4 is XeF 5 + salt. The anionic parts of both spectra are similar. In the system chromium fluorides-krypton difluoride only chromium pentafluoride is obtained. A new method [3] designed for the preparation of polymeric in AHF insoluble binary fluorides was used for the preparation of CrF 4. Its magnetic measurements indicate strong interactions between chromium atoms.

Properties of atoms in molecules: krypton and xenon and their bonds to nitrogen and fluorine in hydrogen cyanide complexes with noble gas fluorides, HCN-NgF+, NgF+ and NgF2 (Ng = noble gas)

Etudes experimentale et theorique des proprietes des liaisons formees entre N, F et Kr, Xe. La capacite des ions KrF + et XeF + a agir comme des acides de Lewis est reliee a la presence de trous dans les distributions de charge de la couche de valence des atomes Kr et Xe. Etude du mecanisme de formation des liaisons Kr−N et Xe−N dans les composes d'addition de KrF + et XeF + avec HCN

Reactions of oxo anions with halogen and noble gas fluorides

Reactions of oxo anions with halogen and noble gas fluorides

Developments in inorganic fluorine chemistry through noble-gas chemistry

The discovery of noble-gas compounds in 1962 quickly led to the isolation of four new simple fluorides, XeF 2, XeF 4, XeF 6 and KrF 2. All are clean fluorinating agents and this was recognized from the beginning [1]. Two have turned out to be particularly useful. Xenon difluoride has been extensively used in organic chemistry [2] and has also been instrumental in the development of new classes of inorganic compounds such as the transition-metal carbonyl fluorides [3] and chalcogenide fluorides [4]. Krypton difluoride has yielded new high oxidation-state fluorides and fluoride ions such as AuF 5 [5] and [BrF 6] + [6]. The value and further potential of noble-gas fluorides, especially XeF 2 and KrF 2, as fluorinating agents will be discussed.

Tc(VII) oxyfluorides; Preparation and study by 99Tc NMR, raman spectroscopy and x-ray crystallography

Although TcO 3F can be prepared by solvolysis of TcO 4 − in anhydrous HF and ReO 2F 3 and ReOF 5 have been known for some time, the preparations of the higher oxyfluorides of Tc(VII) have not been reported. The noble-gas fluorides KrF 2 and XeF 6 are potent oxidative fluorinating agents and provide a ready means to the syntheses of the higher oxyfluorides of Tc(VII). Thus, XeF 6 and KrF 2 oxidative fluorinations of TcO 3F in HF media lead to the stepwise elimination of O 2 gas and fluorination of Tc(VII), resulting in the syntheses of TcO 2F 3 and Tc 2O 5F 4. The latter is the subJect of a x-ray single crystal structure and vibrational study. Technetium-99 NMR spectroscopy has been used to monitor the above reactions and to characterize the diamagnetic Tc(VII) products in solution. Technetium-99 possesses a quadrupole moment, Q (I = 9/2). Quadrupole relaxation is expected to broaden 99Tc NMR signals, but due to the favorable magnitude of Q and large I, the extent of line broadening is not severe. In the case of TcO 2F 3, the line width is narrow enough in the non-cubic environment of 99Tc to permit the observation of the first 99Tc- 19F spin-spin coupling. The fluoride ion donor properties of TcO 3F are also reported, leading to the isolation of TcO 3F·AsF 5 from HF solution. 99Tc and 17O NMR studes confirm the presence of TcO 3 + in solution. Solid stare Raman spectroscopy indicates that the TcO 3 + cation is fluorine bridged to the AsF 6 − anion.

The preparation of technetium oxyfluorides and their characterization by 99Tc, 17O and 19F NMR spectroscopy

Relatively little is known about the chemistry of technetium, especially in its highest oxidation state. At the same time, 99Tc (I=9/2, Q=−0.19 × 10−24cm 2) is one of the more sensitive NMR nuclei (sensitivity relative to the proton is 0.275 at 100% abundance). Pertechnetate, TcO 4 −, the standard for 99Tc NMR spectroscopy, also displays primary isotopic shifts for 17O- and 18O-enriched samples. Technetium-99 NMR has proven an invaluable structural probe in the study of Tc(VII) oxyfluorides. Noble gas fluorides (KrF 2 and XeF 6) have been used to synthesize novel Tc(VII) species from solutions of TcO 3F in anhydrous HF, i.e. Tc 2O 5F 4 and TcO 2F 3. Pertechnetyl fluoride has also been prepared and its fluoride ion donor properties studied in HF solution. Solid TcO 3 +AsF 6 − has been isolated from these solutions and characterized. In addition to 99Tc NMR, compounds have also been studied by 19F and 17O (enriched) NMR spectroscopy.

Lasers and fluorine chemistry: A few illustrative studies

Following a brief survey of the current work on fluorine and lasers, the main results of studies performed in out laboratory concerning laser photochemistry, fluorine generators for chemical lasers and electronic transition gas lasers will be presented. The laser photochemistry study was achieved using isotopic selective excitation of the 35ClF molecule and the observed isotopic effect allowed us to obtain information oh the photo-induced reaction with sulfur tetrafluoride. Some tetrafluoroammonium salts which may be considered as potential solid sources of fluorine for chemical lasers, were studied mainly from a thermochemical point of view. Results concerning their decomposition, solid state phase change and resulting formation enthalpy were obtained. As far as the electronic transition gas lasers are concerned, a higly corrosion resistant experimental set up has been used to study the chemical behavior of halogens or noble gas fluorides under electric discharge regime and to obtain information on the processes involved.

ChemInform Abstract: A RAMAN SPECTROSCOPIC STUDY OF NOBLE GAS FLUORIDE ADDUCT FORMATION WITH BISMUTH PENTAFLUORIDE

AbstractDie Addukte (I)‐(VI) sowie das Salz (VII) werden in HF und im Falle (V) in BrF 5 als Lösungsmittel dargestellt und mittels Tieftemp.‐Raman‐Spektroskopie charakterisiert.

A Raman spectroscopic study of noble-gas fluoride adduct formation with bismuth pentafluoride

The fluoride-ion acceptor properties of BiF5 have been assessed by the preparation of several new adducts of the binary noble-gas fluroides with BiF5. The adducts XeF4·BiF5, XeF4·2BiF5, XeF2·BiF5, XeF2·2BiF5, 2XeF2·BiF5, KrF2·BiF5, and Cs[Bi2F11] have been prepared and characterized by low-temperature Raman spectroscopy. Although the compounds may be described as ionic to a first approximation, there are rather strong fluoride-bridge interactions between the respective cation and the anion which suggest substantial covalent contributions to the bonding. The present study complements previous studies of adducts between the noble-gas fluorides and AsF5 and SbF5. The strength of the cation–anion interactions can be taken as a measure of the acidity of the pentafluoride. It is shown that BiF5 is a much weaker Lewis acid than SbF5.