Xenon Trioxide Coordination Complexes of Crown Ethers: (CH2CH2O)4XeO3, and Xe(VI) Hydrates [(CH2CH2O)6(H2O)XeO3]∙H2O and [(CH2CH2O)6(H2O)XeO3]2∙2H2O∙HF.

Following our report of the first coordination complex between a noble-gas compound and a crown ether, (CH2CH2O)5XeO3, the reactions and structures of XeO3 complexes with 12-crown-4 and 18-crown-6 were investigated. The reactions of 12-crown-4 and 18-crown-6 with XeO3 in dilute aqueous HF solutions yielded (CH2CH2O)4XeO3 and [(CH2CH2O)6(H2O)XeO3]2∙2H2O∙HF, whereas reactions of 12-crown-4 and 18-crown-6 in acetone solutions with moist solid XeO3 yielded (CH2CH2O)4XeO3 and [(CH2CH2O)6(H2O)XeO3]∙H2O. The (CH2CH2O)4XeO3 and [(CH2CH2O)6(H2O)XeO3]∙H2O complexes are air-stable and shock-insensitive, whereas [(CH2CH2O)6(H2O)XeO3]2∙2H2O∙HF is a treacherous, shock-sensitive detonator.

Chromium(VI) Oxyfluoride Dianions, [Cr O F ] and [CrO F ] ; Syntheses and Structures of [XeF ] [Cr O F ], [XeF ] [Cr O F ] ⋅ nX (X=HF, n=4; X=XeOF , n=2), and [XeF ][Xe F ][CrO F ].

The fluorobasic character of the strong oxidative fluorinator, XeF , and the oxidative resistance of the [XeF ] and [Xe F ] cations have been exploited for the syntheses of several novel Cr(VI) dianion salts. The reactions of XeF and CrO F in anhydrous HF and by direct fusion of the reactants in melts have yielded the first dinuclear Cr(VI) oxyfluoro-dianion salts, [XeF ] [Cr O F ], [XeF ] [Cr O F ] ⋅ 4HF, [XeF ] [Cr O F ] ⋅ 2XeOF , and mononuclear Cr(VI) oxyfluoro-dianion salt, [XeF ][Xe F ][CrO F ]. The salts were structurally characterized by low-temperature (LT) single-crystal X-ray diffraction (SCXRD) and LT Raman spectroscopy.

XeF Coordination Complexes of the [BrO] Cation, [OBr(FXeF)][AsF] ( = 1, 2) and [OBr(FXeF)][SbF]; Their Syntheses and Structural Characterizations.

The syntheses and structural characterizations of the first XeF coordination complexes of the [BrO] cation are described. The reactions of [BrO][PnF] (Pn = As, Sb) with XeF in anhydrous HF solvent yield the salts [OBr(FXeF)][AsF] ( = 1, 2) and [OBr(FXeF)][SbF], which were characterized by low-temperature (LT) Raman spectroscopy and single-crystal X-ray diffraction (SCXRD). The XeF ligands and [PnF] coordinate to the Lewis acidic [BrO] cation through primarily electrostatic Br---F σ-hole bonds that result from coordination of the F atoms into regions of high positive electrostatic potential on the Br(V) atom and have bond trajectories that avoid the stereoactive valence electron lone-pair of Br(V).

Synthesis, Structure, and Bonding of a Xe Transition-Metal Coordination Complex, F XeF - - -WOF.

The coordination complex, F XeF - - -WOF , was synthesized in CFCl solvent by reaction of the weak fluoride-ion donor and strong oxidative fluorinating agent, XeF , with the moderate-strength fluoride-ion acceptor, WOF . The compound is the only transition-metal coordination complex of Xe and was characterized at low temperatures by single-crystal X-ray diffraction and Raman spectroscopy. Xenon tetrafluoride and WOF coordinate trans to the W=O bond through a W- - -F bond.

Noble-Gas Difluoride Complexes of MOF (M=Mo, W); Syntheses, Structures and Bonding of NgF ⋅ MOF and XeF ⋅ 2MOF (Ng=Kr, Xe).

The NgF  ⋅ MOF (Ng=Kr, Xe; M=Mo, W) and XeF  ⋅ 2MOF complexes were synthesized in anhydrous HF (aHF) solvent and melts, respectively. Their single-crystal X-ray diffraction (SCXRD) structures show NgF  ⋅ MOF and XeF  ⋅ 2MOF have F -Ng-F - - -M arrangements, in which the NgF ligands coordinate to MOF through Ng-F - - -M bridges. The XeF ligands of XeF  ⋅ 2MOF also coordinate to F OM-F '- - -M'OF moieties through Xe-F - - -M bridges to form F -Xe-F - - -M(OF )-F '- - -M'OF , where XeF coordinates trans to the M=O bond and F ' coordinates trans to the M'=O bond.

Syntheses and Characterizations of the Mixed Noble-Gas Compounds, [FKr FXe F][AsF ]⋅0.5 Kr F ⋅2 HF, ([Kr F ][AsF ]) ⋅Xe F , and Xe F ⋅Kr F.

Reaction of [XeF][AsF ] with excess KrF at -78 °C in anhydrous HF (aHF) solvent has yielded the first mixed Kr /Xe noble-gas compound, [FKrFXeF][AsF ] ⋅0.5 KrF ⋅2 HF, a salt of the [FKrFXeF] cation. The potent oxidative fluorinating properties of Kr fluoride species resulted in oxidation of Xe to Xe in aHF at -60 °C to form the mixed Kr /Xe cocrystals, ([Kr F ][AsF ]) ⋅XeF and XeF ⋅KrF .

Mixed Noble-Gas Compounds of Krypton(II) and Xenon(VI); [F Xe(FKrF)AsF ] and [F Xe(FKrF) AsF ].

The coordination chemistry of KrF has been limited in contrast with that of XeF , which exhibits a far richer coordination chemistry with main-group and transition-metal cations. In the present work, reactions of [XeF ][AsF ] with KrF in anhydrous HF solvent afforded [F Xe(FKrF)AsF ] and [F Xe(FKrF) AsF ], the first mixed krypton/xenon compounds. X-ray crystal structures and Raman spectra show the KrF ligands and [AsF ] anions are F-coordinated to the xenon atoms of the [XeF ] cations.

Group 6 Oxyfluoro-Anion Salts of [XeF ] and [Xe F ] : Syntheses and Structures of [XeF ][M O F ] (M=Mo, W), [Xe F ][M'OF ] (M'=Cr, Mo, W), [XeF ][HF ]⋅CrOF , and [XeF ][WOF ]⋅XeOF.

The reactions of the fluoride-ion donor, XeF , with the fluoride-ion acceptors, M'OF (M'=Cr, Mo, W), yield [XeF ] and [Xe F ] salts of [M'OF ] and [M O F ] (M=Mo, W). Xenon hexafluoride and MOF react in anhydrous hydrogen fluoride (aHF) to give equilibrium mixtures of [Xe F ] , [XeF ] , [(HF) F] , [MOF ] , and [M O F ] from which the title salts were crystallized. The [XeF ][CrOF ] and [Xe F ][CrOF ] salts could not be formed from mixtures of CrOF and XeF in aHF at low temperature (LT) owing to the low fluoride-ion affinity of CrOF , but yielded [XeF ][HF ]⋅CrOF instead.

Metal Hydride Vibrations: The Trans Effect of the Hydride.

-Dihydride complexes are important in many homogeneous catalytic processes. Here vibrational spectroscopy and density functional theory (DFT) methods are used for the first time to reveal that 4d and 5d metals transmit more effectively than the 3d metals influence of the ligand trans to the hydride and also couple the motions of the -hydrides more effectively. This property of the metal is linked to higher hydride reactivity.

Chromium Oxide Tetrafluoride and Its Reactions with Xenon Hexafluoride; the [XeF ] and [Xe F ] Salts of the [Cr OF ] , [Cr OF ] , [Cr O F ] , and [Cr F ] Anions.

Molten mixtures of XeF and Cr OF react by means of F elimination to form [XeF ][Xe F ][Cr OF ]⋅2 Cr OF , [XeF ] [Cr F ]⋅2 Cr OF , [Xe F ] [Cr F ], and [XeF ] [Cr O F ], whereas their reactions in anhydrous hydrogen fluoride (aHF) and CFCl /aHF yield [XeF ] [Cr O F ]⋅2 HF and [XeF ] [Cr O F ]⋅2 XeOF . Other than [Xe F ][M OF ] and [XeF ][M O F ] (M=Mo or W), these salts are the only Group 6 oxyfluoro-anions known to stabilize noble-gas cations. Their reaction pathways involve redox transformations that give [XeF ] and/or [Xe F ] salts of the known [Cr OF ] and [Cr F ] anions, and the novel [Cr O F ] anion.

Xenon Trioxide Adducts of O-Donor Ligands; [(CH ) CO] XeO , [(CH ) SO] (XeO ) , (C H NO) (XeO ) , and [(C H ) PO] XeO.

Xenon trioxide (XeO ) forms adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone by coordination of the ligand oxygen atoms to the Xe atom of XeO . The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction, and Raman spectroscopy. Unlike solid XeO , which detonates when mechanically or thermally shocked, solid (C H NO) (XeO ) , [(C H ) PO] XeO , and [(CH ) SO] (XeO ) are insensitive to mechanical shock.

Syntheses, Structures, and Bonding of NgF ⋅CrOF , NgF ⋅2CrOF (Ng=Kr, Xe), and (CrOF ).

The noble-gas difluoride adducts, NgF ⋅CrOF and NgF ⋅2CrOF (Ng=Kr and Xe), have been synthesized and structurally characterized at low temperatures by Raman spectroscopy and single-crystal X-ray diffraction. The low fluoride ion affinity of CrOF renders it incapable of inducing fluoride ion transfer from NgF (Ng=Kr and Xe) to form ion-paired salts of the [NgF] cations having either the [CrOF ] or [Cr O F ] anions. The crystal structures show the NgF ⋅CrOF adducts are comprised of F -Ng-F - - -Cr(O)F structural units in which NgF is weakly coordinated to CrOF by means of a fluorine bridge, F , in which Ng-F is elongated relative to the terminal Ng-F bond.

A Homoleptic KrF Complex, [Hg(KrF ) ][AsF ] ⋅2 HF.

The reaction of Hg(AsF ) with a large molar excess of KrF in anhydrous HF has afforded the first homoleptic KrF coordination complex of a metal cation, [Hg(KrF ) ][AsF ] ⋅2 HF. The [Hg(KrF ) ] dication is well-isolated in the low-temperature crystal structure of its HF-solvated [AsF ] salt, and consists of eight KrF molecules that are terminally coordinated to Hg by means of Hg-F(KrF) bonds to form a slightly distorted, square-antiprismatic coordination sphere around mercury. The Raman spectrum of [Hg(KrF ) ] was assigned with the aid of calculated gas-phase vibrational frequencies.

A Stable Crown Ether Complex with a Noble-Gas Compound.

Crown ethers have been known for over 50 years, but no example of a complex between a noble-gas compound and a crown ether or another polydentate ligand had previously been reported. Xenon trioxide is shown to react with 15-crown-5 to form the kinetically stable (CH CH O) XeO adduct, which, in marked contrast with solid XeO , does not detonate when mechanically shocked. The crystal structure shows that the five oxygen atoms of the crown ether are coordinated to the xenon atom of XeO .

Stable Chloro- and Bromoxenate Cage Anions; [X(XeO)] and [X(XeO)] (X = Cl or Br).

The number of isolable compounds which contain different noble-gas-element bonds is limited for xenon and even more so for krypton. Examples of Xe-Cl bonds are rare, and prior to this work, no Xe-Br bonded compound had been isolated in macroscopic quantities. The syntheses, isolation, and characterization of the first compounds to contain Xe-Br bonds and their chlorine analogues are described in the present work.

Coordination of KrF to a Naked Metal Cation, Mg.

Examples of coordination compounds in which KrF functions as a ligand are very rare. In contrast, XeF provides a rich coordination chemistry with a variety of main-group and transition metal cations. The reactions of Mg(AsF ) and KrF in HF or BrF solvent have afforded [Mg(KrF ) (AsF ) ] and [Mg(KrF ) (AsF ) ]⋅2 BrF , respectively, the first examples of a metal cation ligated by KrF .

Solid-State Structures of XeO.

The solid-state structure of xenon trioxide, XeO, was reinvestigated by low-temperature single-crystal X-ray diffraction and shown to exhibit polymorphism that is dependent on the crystallization conditions. The previously reported α-phase (orthorhombic, P222) only forms upon evaporation of aqueous HF solutions of XeO. In contrast, two new phases, β-XeO (rhombohedral, R3) and γ-XeO (rhombohedral, R3c), have been obtained by slow evaporation of aqueous solutions of XeO.

Syntheses and Structures of Xenon Trioxide Alkylnitrile Adducts.

The potent oxidizer and highly shock-sensitive binary noble-gas oxide XeO interacts with CH CN and CH CH CN to form O XeNCCH , O Xe(NCCH ) , O XeNCCH CH , and O Xe(NCCH CH ) . Their low-temperature single-crystal X-ray structures show that the xenon atoms are consistently coordinated to three donor atoms, which results in pseudo-octahedral environments around the xenon atoms. The adduct series provides the first examples of a neutral xenon oxide bound to nitrogen bases.

Synthesis and Characterization of [XeOXe](2+) in the Adduct-Cation Salt, [CH3 CN- - -XeOXe- - -NCCH3 ][AsF6 ]2.

Acetonitrile and [FXeOXe- - -FXeF][AsF6 ] react at -60 °C in anhydrous HF (aHF) to form the CH3 CN adduct of the previously unknown [XeOXe](2+) cation. The low-temperature X-ray structure of [CH3 CN- - -XeOXe- - -NCCH3 ][AsF6 ]2 exhibits a well-isolated adduct-cation that has among the shortest Xe-N distances obtained for an sp-hybridized nitrogen base adducted to xenon. The Raman spectrum was fully assigned by comparison with the calculated vibrational frequencies and with the aid of (18) O-enrichment studies.

Nature of the Xe(VI)-N Bonds in F6 XeNCCH3 and F6 Xe(NCCH3)2 and the Stereochemical Activity of Their Xenon Valence Electron Lone Pairs.

The recently reported syntheses and X-ray crystal structures of the highly endothermic compounds F6XeNCCH3 and F6Xe(NCCH3)2 ⋅CH3CN provide the first, albeit weakly covalent, Xe(VI)-N bonds. The XeF6 unit of F6 XeNCCH3 possesses distorted octahedral (C3v ) symmetry similar to gas-phase XeF6 , whereas the XeF6 unit of F6 Xe(NCCH3)2 ⋅CH3CN possesses C2v symmetry. Herein, the natural bond orbital (NBO), atoms in molecules (AIM), electron localization function (ELF), and molecular electrostatic potential surface (MEPS) analyses show that the Xe valence electron lone pairs (VELPs) of both compounds are stereochemically active.

Thiazyl Trifluoride (NSF3) Adducts and Imidodifluorosulfate (F2OSN-) Derivatives of Hg(OTeF5)2.

Reactions of Hg(OTeF5)2 with excess amounts of NSF3 at 0 °C result in the formation of NSF3 adducts having the compositions [Hg(OTeF5)2·N≡SF3]∞ (1), [Hg(OTeF5)2·2N≡SF3]2 (2), and Hg3(OTeF5)6·4N≡SF3 (3). When the reactions are carried out at room temperature, oxygen/fluorine metatheses occur yielding the F2OSN- derivatives [Hg(OTeF5)(N═SOF2)·N≡SF3]∞ (4) and [Hg3(OTeF5)5(N═SOF2)·2N≡SF3]2 (5). The proposed reaction pathway leading to F2OSN- group formation occurs by nucleophilic attack by a F5TeO- group at the sulfur(VI) atom of NSF3, followed by TeF6 elimination.

[XeOXeOXe](2+), the Missing Oxide of Xenon(II); Synthesis, Raman Spectrum, and X-ray Crystal Structure of [XeOXeOXe][μ-F(ReO2F3)2]2.

The [XeOXeOXe](2+) cation provides an unprecedented example of a xenon(II) oxide and a noble-gas oxocation as well as a rare example of a noble-gas dication. The [XeOXeOXe](2+) cation was synthesized as its [μ-F(ReO2F3)2](-) salt by reaction of ReO3F with XeF2 in anhydrous HF at -30 °C. Red-orange [XeOXeOXe][μ-F(ReO2F3)2]2 rapidly decomposes to XeF2, ReO2F3, Xe, and O2 when the solid or its HF solutions are warmed above -20 °C.

Syntheses and Structures of F6 XeNCCH3 and F6 Xe(NCCH3)2.

Acetonitrile and the potent oxidative fluorinating agent XeF6 react at -40 °C in Freon-114 to form the highly energetic, shock-sensitive compounds F6XeNCCH3 (1) and F6Xe(NCCH3)2⋅CH3CN (2⋅CH3CN). Their low-temperature single-crystal X-ray structures show that the adducted XeF6 molecules of these compounds are the most isolated XeF6 moieties thus far encountered in the solid state and also provide the first examples of Xe(VI)-N bonds. The geometry of the XeF6 moiety in 1 is nearly identical to the calculated distorted octahedral (C3v) geometry of gas-phase XeF6.

Ultraviolet photolysis studies on XeO4 in noble-gas and F2 matrices and the formation and characterization of a new Xe(VIII) oxide, (η(2) -O2 )XeO3.

The photolytic behavior of the thermochemically unstable xenon(VIII) oxide XeO4 was investigated by UV irradiation in noble-gas and F2 matrices. Photolysis of Xe(16) O4 or Xe(18) O4 in noble-gas matrices at 365 nm yielded XeO3 and a new xenon(VIII) oxide, namely, (η(2) -O2 )XeO3 , which, along with XeO4 , was characterized by matrix-isolation IR spectroscopy and quantum-chemical calculations. Calculations of the UV spectrum showed that the photodecomposition is induced by an n→σ* transition, but the nature of the excitation differs when different light sources are used.