Fluoride Ion Donor Research Articles

Discrete Mono-, Di-, and Trinuclear Anions [MoOF5]-, [MoVOF5]2-, [MoO2F4]2-, [Mo2O2F9]-, [Mo3O3F13]-, and the Infinite Chain Anion [MoO2F3]- Obtained from Reactions of MoOF4: Synthesis and Analysis of the Structure-Chemical Relations of the Compounds.

The herein-reported oxyfluoridometallate salts were synthesized and structurally characterized during the studies of the Lewis acidity of MOF4 (M = Mo, W) with various fluoride ion donors (RbF, CsF, TlF, AgF, SrF2, BaF2, PbF2) in different solvents (aqHF 48%, aHF, BrF3, ClF3). Phase-pure MoOF4 was either synthesized by hydrolysis of MoF6 with SiO2 in anhydrous HF (aHF) or by reactions of BrF3 with MoO2 or MoO3, respectively. The compound was characterized by infrared and Raman spectroscopy, solid-state quantum-chemical calculations, as well as powder and single-crystal X-ray diffraction. MoOF4 reacted with PbF2 in aHF forming Pb[MoOF5]2, while under comparable conditions, WOF4 formed Pb3[WOF5]4F2, containing the [WOF5]- anion. Salts containing such [MoOF5]- anions were also directly obtained from reactions of BrF3, MoO3, and AF2 (A = Sr, Ba), while with AgF, the compound Ag[Mo2O2F9] was observed. ClF3 reacted with MoO3 to form [ClOF2][Mo3O3F13]. Carrying out similar reactions in aqueous HF (aqHF) in autoclaves under hydrofluorothermal conditions leads to O-richer compounds with the composition A[MoO2F4] (A = Sr, Ba). With RbF or Tl2(CO3), the compounds A[MoO2F3] (A = Rb, Tl) were obtained. With CsF reduction to Mo(V) occurred as Cs2[MoVOF5] was formed. We report on similarities and differences within the respective anions and within the crystal structures of these compounds.

Calix[4]pyrrolato-germane-(thf)2: Unlocking the Anti-van't Hoff-Le Bel Reactivity of Germanium(IV) by Ligand Dissociation.

Anti-van't Hoff-Le Bel configured p-block element species possess intrinsically high reactivity and are thus challenging to isolate. Consequently, numerous elements in this configuration, including square-planar germanium(IV), remain unexplored. Herein, we follow a concept to reach anti-van't Hoff-Le Bel reactivity by ligand dissociation from a rigid calix[4]pyrrole germane in its bis(thf) adduct. While the macrocyclic ligand assures square-planar coordination in the uncomplexed form, the labile thf donors provide robustness for isolation on a multigram scale. Unique properties of a low-lying acceptor orbital imparted to germanium(IV) can be verified, e.g., by isolating an elusive anionic hydrido germanate and exploiting it for challenging bond activations. Aldehydes, water, alcohol, and a CN triple bond are activated for the first time by germanium-ligand cooperativity. Unexpected behaviors against fluoride ion donors disclose critical interferences of a putative redox-coupled fluoride ion transfer during the experimental determination of Lewis acidity. Overall, we showcase how ligand lability grants access to the uncharted chemistry of anti-van't Hoff-Le Bel germanium(IV) and line up this element as a member in the emerging class of structurally constrained p-block elements.

Synthesis, Structure, and Bonding of a XeIV Transition-Metal Coordination Complex, F3 XeFb - - -WOF4.

The coordination complex, F3 XeFb - - -WOF4 , was synthesized in CFCl3 solvent by reaction of the weak fluoride-ion donor and strong oxidative fluorinating agent, XeF4 , with the moderate-strength fluoride-ion acceptor, WOF4 . The compound is the only transition-metal coordination complex of XeIV and was characterized at low temperatures by single-crystal X-ray diffraction and Raman spectroscopy. Xenon tetrafluoride and WOF4 coordinate trans to the W=O bond through a W- - -Fb bond. The XeF3 moiety of F3 XeFb - - -WOF4 acquires a degree of [XeF3 ]+ character upon coordination that is reflected by its Xe-F stretching frequencies which are intermediate with respect to those of XeF4 and [XeF3 ]+ . Calculations show W- - -Fb is predominantly an electrostatic, σ-hole bond with a significant orbital contribution that accounts for the bent Xe-Fb - - -W angle. The calculations show F3 XeFb - - -MOF4 (M=Cr, Mo) are less stable than their W analogue, consistent with failed attempts to synthesize F3 XeFb - - -MoOF4 .

Noble-Gas Chemistry More than Half a Century after the First Report of the Noble-Gas Compound.

Recent development in the synthesis and characterization of noble-gas compounds is reviewed, i.e., noble-gas chemistry reported in the last five years with emphasis on the publications issued after 2017. XeF2 is commercially available and has a wider practical application both in the laboratory use and in the industry. As a ligand it can coordinate to metal centers resulting in [M(XeF2)x]n+ salts. With strong Lewis acids, XeF2 acts as a fluoride ion donor forming [XeF]+ or [Xe2F3]+ salts. Latest examples are [Xe2F3][RuF6]·XeF2, [Xe2F3][RuF6] and [Xe2F3][IrF6]. Adducts NgF2·CrOF4 and NgF2·2CrOF4 (Ng = Xe, Kr) were synthesized and structurally characterized at low temperatures. The geometry of XeF6 was studied in solid argon and neon matrices. Xenon hexafluoride is a well-known fluoride ion donor forming various [XeF5]+ and [Xe2F11]+ salts. A large number of crystal structures of previously known or new [XeF5]+ and [Xe2F11]+ salts were reported, i.e., [Xe2F11][SbF6], [XeF5][SbF6], [XeF5][Sb2F11], [XeF5][BF4], [XeF5][TiF5], [XeF5]5[Ti10F45], [XeF5][Ti3F13], [XeF5]2[MnF6], [XeF5][MnF5], [XeF5]4[Mn8F36], [Xe2F11]2[SnF6], [Xe2F11]2[PbF6], [XeF5]4[Sn5F24], [XeF5][Xe2F11][CrVOF5]·2CrVIOF4, [XeF5]2[CrIVF6]·2CrVIOF4, [Xe2F11]2[CrIVF6], [XeF5]2[CrV2O2F8], [XeF5]2[CrV2O2F8]·2HF, [XeF5]2[CrV2O2F8]·2XeOF4, A[XeF5][SbF6]2 (A = Rb, Cs), Cs[XeF5][BixSb1-xF6]2 (x = ~0.37–0.39), NO2XeF5(SbF6)2, XeF5M(SbF6)3 (M = Ni, Mg, Zn, Co, Cu, Mn and Pd) and (XeF5)3[Hg(HF)]2(SbF6)7. Despite its extreme sensitivity, many new XeO3 adducts were synthesized, i.e., the 15-crown adduct of XeO3, adducts of XeO3 with triphenylphosphine oxide, dimethylsulfoxide and pyridine-N-oxide, and adducts between XeO3 and N-bases (pyridine and 4-dimethylaminopyridine). [Hg(KrF2)8][AsF6]2·2HF is a new example of a compound in which KrF2 serves as a ligand. Numerous new charged species of noble gases were reported (ArCH2+, ArOH+, [ArB3O4]+, [ArB3O5]+, [ArB4O6]+, [ArB5O7]+, [B12(CN)11Ne]−). Molecular ion HeH+ was finally detected in interstellar space. The discoveries of Na2He and ArNi at high pressure were reported. Bonding motifs in noble-gas compounds are briefly commented on in the last paragraph of this review.

Group 6 Oxyfluoro-Anion Salts of [XeF5 ]+ and [Xe2 F11 ]+ : Syntheses and Structures of [XeF5 ][M2 O2 F9 ] (M=Mo, W), [Xe2 F11 ][M'OF5 ] (M'=Cr, Mo, W), [XeF5 ][HF2 ]⋅CrOF4 , and [XeF5 ][WOF5 ]⋅XeOF4.

The reactions of the fluoride-ion donor, XeF6 , with the fluoride-ion acceptors, M'OF4 (M'=Cr, Mo, W), yield [XeF5 ]+ and [Xe2 F11 ]+ salts of [M'OF5 ]- and [M2 O2 F9 ]- (M=Mo, W). Xenon hexafluoride and MOF4 react in anhydrous hydrogen fluoride (aHF) to give equilibrium mixtures of [Xe2 F11 ]+ , [XeF5 ]+ , [(HF)n F]- , [MOF5 ]- , and [M2 O2 F9 ]- from which the title salts were crystallized. The [XeF5 ][CrOF5 ] and [Xe2 F11 ][CrOF5 ] salts could not be formed from mixtures of CrOF4 and XeF6 in aHF at low temperature (LT) owing to the low fluoride-ion affinity of CrOF4 , but yielded [XeF5 ][HF2 ]⋅CrOF4 instead. In contrast, MoOF4 and WOF4 are sufficiently Lewis acidic to abstract F- ion from [(HF)n F]- in aHF to give the [MOF5 ]- and [M2 O2 F9 ]- salts of [XeF5 ]+ and [Xe2 F11 ]+ . To circumvent [(HF)n F]- formation, [Xe2 F11 ][CrOF5 ] was synthesized at LT in CF2 ClCF2 Cl solvent. The salts were characterized by LT Raman spectroscopy and LT single-crystal X-ray diffraction, which provided the first X-ray crystal structure of the [CrOF5 ]- anion and high-precision geometric parameters for [MOF5 ]- and [M2 O2 F9 ]- . Hydrolysis of [Xe2 F11 ][WOF5 ] by water contaminant in HF solvent yielded [XeF5 ][WOF5 ]⋅XeOF4 . Quantum-chemical calculations were carried out for M'OF4 , [M'OF5 ]- , [M'2 O2 F9 ]- , {[Xe2 F11 ][CrOF5 ]}2 , [Xe2 F11 ][MOF5 ], and {[XeF5 ][M2 O2 F9 ]}2 to obtain their gas-phase geometries and vibrational frequencies to aid in their vibrational mode assignments and to assess chemical bonding.

Stabilization of [WF5 ]+ by Bidentate N-Donor Ligands.

Transition-metal hexafluorides do not exhibit fluoride-ion donor properties in the absence of donor ligands. We report the first synthesis of donor-stabilized [MF5 ]+ derived from a transition-metal hexafluoride via fluoride-ion abstraction using WF6 (L) (L=2,2'-bipy, 1,10-phen) and SbF5 (OSO) in SO2 . The [WF5 (L)][Sb2 F11 ] salts and [WF5 (1,10-phen)][SbF6 ]⋅SO2 have been characterized by X-ray crystallography, Raman spectroscopy, and multinuclear NMR spectroscopy. The reaction of WF6 (2,2'-bipy) with an equimolar amount of SbF5 (OSO) reveals an equilibrium between [WF5 (2,2'-bipy)]+ and the [WF4 (2,2'-bipy)2 ]2+ dication, as determined by 19 F NMR spectroscopy. The geometries of the cations in the solid state are reproduced by gas-phase geometry optimizations (DFT-B3LYP), and NBO analyses reveal that the positive charges of the cations are stabilized primarily by compensatory σ-electron donation from the N-donor ligands.

X-ray Crystal Structures of [XeF][MF6] (M = As, Sb, Bi), [XeF][M2F11] (M = Sb, Bi) and Estimated Thermochemical Data and Predicted Stabilities for Noble-Gas Fluorocation Salts using Volume-Based Thermodynamics

The crystal structures of the xenon(II) salts, [XeF][SbF(6)], [XeF][BiF(6)], and [XeF][Bi(2)F(11)], have been determined for the first time, and those of XeF(2), [XeF][AsF(6)], [XeF][Sb(2)F(11)], and [XeF(3)][Sb(2)F(11)] have been redetermined with greater precision at -173 °C. The Bi(2)F(11)(-) anion, which has a structure analogous to those of the As(2)F(11)(-) and Sb(2)F(11)(-) anions, has been structurally characterized by single crystal X-ray diffraction for the first time as its XeF(+) salt. The fluorine bridge between the bismuth atoms is asymmetric with Bi---F(b) bond lengths of 2.092(6) and 2.195(6) A and a Bi---F(b)'---Bi bridge bond angle of 145.3(3)°. The XeF(+) cations interact with their anions by means of Xe---F(b)---M bridges. Consequently, the solid-state Raman spectra of [XeF][MF(6)] (M = As, Sb, Bi) were modeled as the gas-phase ion pairs and assigned with the aid of quantum-chemical calculations. Relationships among the terminal Xe-F(t) and bridge Xe---F(b) bond lengths and stretching frequencies and the gas-phase fluoride ion affinities of the parent Lewis acid that the anion is derived from are considered. The analogous krypton ion pairs, [KrF][MF(6)] (M = As, Sb, Bi) were also calculated and compared with their previously published X-ray crystal structures. The calculated cation-anion charge separations indicate that the [XeF][MF(6)] salts are more ionic than their krypton analogues and that XeF(2) is a stronger fluoride ion donor than KrF(2). The lattice energies, standard enthalpies, and free energies of formation for salts containing the NgF(+), Ng(2)F(3)(+), XeF(3)(+), XeF(5)(+), Xe(2)F(11)(+), and XeOF(3)(+) (Ng = Ar, Kr, Xe) cations were estimated using volume-based thermodynamics (VBT) based on crystallographic and estimated ion volumes. These estimated parameters were then used to predict the stabilities of noble-gas salts. VBT is used to examine and predict the stabilities of, inter alia, the salts [XeF(m)][Sb(n)F(5n+1)] and [XeF(m)][As(n)F(5n+1)] (m = 1, 3; n = 1, 2). VBT also confirms that XeF(+) salts are stable toward redox decomposition to Ng, F(2), and MF(5) (M = As, Sb), whereas the isolable krypton compounds and the unknown ArF(+) salts are predicted to be unstable by VBT with the ArF(+) salts being the least stable.

ChemInform Abstract: Fluoride Ion Donor Properties of TcO2F3 and ReO2F3: X-Ray Crystal Structures of MO2F3×SbF5 (M: Tc, Re) and TcO2F3×XeO2F2 and Raman and NMR Spectroscopic Characterization of MO2F3×PnF5 (Pn: As, Sb), [ReO2F2(CH3CN)2] [SbF6], and [Re2O4F

The fluoride ion donor properties of TcO2F3 and ReO2F3 toward AsF5, SbF5, and XeO2F2 have been investigated, leading to the formation of TcO2F3.PnF5 and ReO2F3.PnF5 (Pn = As, Sb) and TcO2F3.XeO2F2, which were characterized in the solid state by Raman spectroscopy and X-ray crystallography. TcO2F3.SbF5 crystallizes in the monoclinic system P2(1)/n, with a = 7.366(2) A, b = 10.441(2) A, c = 9.398(2) A, beta = 93.32(3) degrees, V = 721.6(3) A3, and Z = 4 at 24 degrees C, R1 = 0.0649, and wR2 = 0.1112. ReO2F3.SbF5 crystallizes in the monoclinic system P2(1)/c, with a = 5.479(1) A, b = 10.040(2) A, c = 12.426(2) A, beta = 99.01(3) degrees, V = 675.1(2) A3, and Z = 4 at -50 degrees C, R1 = 0.0533, and wR2 = 0.1158. TcO2F3.XeO2F2 crystallizes in the orthorhombic system Cmc2(1), with a = 7.895(2) A, b = 16.204(3) A, c = 5.198(1) A, beta = 90 degrees, V = 665.0(2) A3, and Z = 4 at 24 degrees C, R1 = 0.0402, and wR2 = 0.0822. The structures of TcO2F3.SbF5 and ReO2F3.SbF5 consist of infinite chains of alternating MO2F4 and SbF6 units in which the bridging fluorine atoms on the antimony are trans to each other. The structure of TcO2F3.XeO2F2 comprises two distinct fluorine-bridged chains, one of TcO2F3 and the other of XeO2F2 bridged by long Tc-F...Xe contacts. The oxygen atoms of the group 7 metals in the three structures are cis to each other and to two terminal fluorine atoms and trans to the bridging fluorine atoms. The 19F NMR and Raman spectra of TcO2F3.PnF5 and ReO2F3.PnF5 in SbF5 and PnF5-acidified HF solvents are consistent with dissociation of the adducts into cis-MO2F2(HF)2+ cations and PnF6- anions. The energy-minimized geometries of the free MO2F2+ cations and their HF adducts, cis-MO2F2(HF)2+, have been calculated by local density functional theory (LDFT), and the calculated vibrational frequencies have been used as an aid in the assignment of the Raman spectra of the solid MO2F3.PnF5 adducts and their PnF5-acidified HF solutions. In contrast, ReO2F3.SbF5 ionizes in SO2ClF solvent to give the novel Re2O4F5+ cation and Sb2F11- anion. The 19F NMR spectrum of the cation is consistent with two ReO2F2 units joined by a fluorine bridge in which the oxygen atoms are assumed to lie in the equatorial plane. The [ReO2F2(CH3CN)2][SbF6] salt was formed upon dissolution of ReO2F3.SbF5 in CH3CN and was characterized by 1H, 13C, and 19F NMR and Raman spectroscopies. The ReO2F2(CH3CN)2+ cation is a pseudooctahedral cis-dioxo arrangement in which the CH3CN ligands are trans to the oxygens and the fluorines are trans to each other.

Fluoride Ion Donor Properties of cis-OsO2F4: Synthesis, Raman Spectroscopic Study, and X-ray Crystal Structure of [OsO2F3][Sb2F11

The salt, [OsO(2)F(3)][Sb(2)F(11)], has been synthesized by dissolution of cis-OsO(2)F(4) in liquid SbF(5), followed by removal of excess SbF(5) at 0 degrees C to yield orange, crystalline [OsO(2)F(3)][Sb(2)F(11)]. The X-ray crystal structure (-173 degrees C) consists of an OsO(2)F(3)(+) cation fluorine bridged to an Sb(2)F(11)(-) anion. The light atoms of OsO(2)F(3)(+) and the bridging fluorine atom form a distorted octahedron around osmium in which the osmium atom is displaced from its center toward an oxygen atom and away from the trans-fluorine bridge atom. As in other transition metal dioxofluorides, the oxygen ligands are cis to one another and the fluorine bridge atom is trans to an oxygen ligand and cis to the remaining oxygen ligand. The Raman spectrum (-150 degrees C) of solid [OsO(2)F(3)][Sb(2)F(11)] was assigned on the basis of the ion pair observed in the low-temperature crystal structure. Under dynamic vacuum, [OsO(2)F(3)][Sb(2)F(11)] loses SbF(5), yielding the known [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)] salt with no evidence for [OsO(2)F(3)][SbF(6)] formation. Attempts to synthesize [OsO(2)F(3)][SbF(6)] by the reaction of [OsO(2)F(3)][Sb(2)F(11)] with an equimolar amount of cis-OsO(2)F(4) or by a 1:1 stoichiometric reaction of cis-OsO(2)F(4) with SbF(5) in anhydrous HF yielded only [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)]. Quantum-chemical calculations at the SVWN and B3LYP levels of theory and natural bond orbital analyses were used to calculate the gas-phase geometries, vibrational frequencies, natural population analysis charges, bond orders, and valencies of OsO(2)F(3)(+), [OsO(2)F(3)][Sb(2)F(11)], [OsO(2)F(3)][SbF(6)], and Sb(2)F(11)(-). The relative thermochemical stabilities of [OsO(2)F(3)][SbF(6)], [OsO(2)F(3)][Sb(2)F(11)], [OsO(2)F(3)][AsF(6)], [mu-F(OsO(2)F(3))(2)][SbF(6)], [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)], and [mu-F(OsO(2)F(3))(2)][AsF(6)] were assessed using the appropriate Born-Haber cycles to account for the preference for [mu-F(OsO(2)F(3))(2)][Sb(2)F(11)] formation over [OsO(2)F(3)][SbF(6)] formation and for the inability to synthesize [OsO(2)F(3)][SbF(6)].

Synthesis and Characterization of Salts Containing the BrO3F2- Anion; A Rare Example of a Bromine(VII) Species

The BrO(3)F(2)(-) anion has been prepared by reaction of BrO(3)F with the fluoride ion donors KF, RbF, CsF, [N(CH(3))(4)][F], and NOF. The BrO(3)F(2)(-) anion is only the fourth Br(VII) species to have been isolated in macroscopic quantities, and it is one of only three oxide fluorides that possess D(3)(h)() symmetry, the others being XeO(3)F(2) and OsO(3)F(2). The fluoride ion acceptor properties of BrO(3)F contrast with those of ClO(3)F, which does not react with the strong fluoride ion donor [N(CH(3))(4)][F] to form the analogous ClO(3)F(2)(-) salt. The single-crystal X-ray structures of [NO](2)[BrO(3)F(2)][F] and [N(CH(3))(4)][BrO(3)F(2)] confirm the D(3)(h)() symmetry of the BrO(3)F(2)(-) anion and provide accurate Br-O (1.593(3)-1.610(6) A) and Br-F (1.849(5)-1.827(4) A) bond lengths. The salt, [NO](2)[BrO(3)F(2)][F], is fully ordered, crystallizing in the monoclinic space group, C2/c, with a = 9.892(3) A, b = 12.862(4) A, c = 10.141(4) A, beta = 90.75(2) degrees , V = 12460(7) A(3), Z = 4, and R(1) = 0.0671 at -173 degrees C, whereas [N(CH(3))(4))][BrO(3)F(2)] exhibits a 2-fold disorder of the anion, crystallizing in the tetragonal space group, P4/nmm, with a = 8.5718(7) A, c = 5.8117(6) A, V = 427.02(7) A(3), Z = 2, and R(1) = 0.0314 at -173 degrees C. The (19)F chemical shift of [N(CH(3))(4))][BrO(3)F(2)] in CH(3)CN is 237.0 ppm and is more deshielded than those of the previously investigated Br(VII) species, BrO(3)F and BrF(6)(+). The vibrational frequencies of the BrO(3)F(2)(-) anion were determined by use of Raman and infrared spectroscopy and were assigned with the aid of electronic structure calculations and by analogy with the vibrational assignments reported for XeO(3)F(2) and OsO(3)F(2). The internal and symmetry force constants of BrO(3)F(2)(-) were determined by use of general valence force field and B-matrix methods, respectively, and are compared with those of XeO(3)F(2), OsO(3)F(2), and the unknown ClO(3)F(2)(-) anion. The instability of ClO(3)F(2)(-) relative to BrO(3)F(2)(-) has been investigated by electronic structure calculations and rationalized in terms of atomic charges, Mayer bond orders, and Mayer valencies, and the enthalpies of fluoride ion attachment to BrO(3)F and ClO(3)F.

Quantitative measure for the "nakedness" of fluoride ion sources.

A quantitative measure for the donor strength or "nakedness" of fluoride ion donors is presented. It is based on the free energy change associated with the transfer of a fluoride ion from the donor to a given acceptor molecule. Born-Haber cycle calculations were used to calculate both the free energy and the enthalpy change for this process. The enthalpy change is given by the sum of the fluoride ion affinity of the acceptor (as defined in strict thermodynamic convention) and the lattice energy difference (DeltaU(POT)) between the fluoride ion donor and the salt formed with the acceptor. Because, for a given acceptor, the fluoride affinity has a constant value, the relative enthalpy (and also the corresponding free energy) changes are governed exclusively by the lattice energy differences. In this study, BF(3), PF(5), AsF(5), and SbF(5) were used as the acceptors, and the following seven fluoride ion donors were evaluated: CsF, N(CH(3))(4)F (TMAF), N-methylurotropinium fluoride (MUF), hexamethylguanidinium fluoride (HMGF), hexamethylpiperidinium fluoride (HMPF), N,N,N-trimethyl-1-adamantylammonium fluoride (TMAAF), and hexakis(dimethylamino)phosphazenium fluoride (HDMAPF). Smooth relationships between the enthalpy changes and the molar volumes of the donor cations were found which asymptotically approach constant values for infinitely large cations. Whereas CsF is a relatively poor F(-) donor [(U(POT)(CsF) - U(POT)(CsSbF(6))) = 213 kJ mol(-)(1)], when compared to N(CH(3))(4)F [(U(POT)(TMAF) - U(POT)(TMASbF(6))) = 69 kJ mol(-)(1)], a 4 times larger cation (phosphazenium salt) and an infinitely large cation are required to decrease DeltaU(POT) to 17 and 0 kJ mol(-)(1), respectively. These results clearly demonstrate that very little is gained by increasing the cation size past a certain level and that secondary factors, such as chemical and physical properties, become overriding considerations.

Tris(dimethylamino)oxosulfonium difluorotrimethylsilicate, (Me(2)N)(3)SO(+)Me(3)SiF(2)(-) (TAOS Fluoride).

In the OSF(4)/Me(2)NSiMe(3) system besides the long known Me(2)NS(O)F(3) only the trisubstituted derivative is isolated as (Me(2)N)(3)SO(+)Me(3)SiF(2)(-) (3). Similar to (Me(2)N)(3)S(+)Me(3)SiF(2)(-) compound 3 is an excellent fluoride ion donor. With AsF(5) and HF the corresponding hexafluoroarsenate (Me(2)N)(3)SO(+)AsF(6)(-) (4) and the hydrogen bifluoride (Me(2)N)(3)SO(+)HF(2)(-) (5) are formed in almost quantitative yield. X-ray structure determinations of 3-5 surprisingly showed two different types of structures for the cation. In 3 and 5 this cation has C(3) symmetry, while in the hexafluoroarsenate 4 a (Me(2)N)(3)S(+)-like structure with C(s)() symmetry is determined. The experimental results for (Me(2)N)(3)SO(+) and (Me(2)N)(3)S(+) are compared with theoretical calculations for these cations and their isoelectronic neutral counterparts, the phosphorus amides (Me(2)N)(3)PO and (Me(2)N)(3)P, respectively.

The OsO3F+ and μ-F(OsO3F)2+ Cations: Their Syntheses and Study by Raman and 19F NMR Spectroscopy and Electron Structure Calculations and X-ray Crystal Structures of [OsO3F][PnF6] (Pn = As, Sb), [OsO3F][HF]2[AsF6], [OsO3F][HF][SbF6], and [OsO3F][Sb3F16

The fluoride ion donor properties of OsO(3)F(2) have been investigated. The salts [OsO(3)F][AsF(6)], [OsO(3)F][HF](2)[AsF(6)], mu-F(OsO(3)F)(2)[AsF(6)], [OsO(3)F][HF](2)[SbF(6)], and [OsO(3)F][HF][SbF(6)] have been prepared by reaction of OsO(3)F(2) with AsF(5) and SbF(5) in HF solvent and have been characterized in the solid state by Raman spectroscopy. The single-crystal X-ray diffraction studies of [OsO(3)F][AsF(6)] (P2(1)/n, a = 7.0001(11) A, c = 8.8629(13) A, beta = 92.270(7) degrees, Z = 4, and R(1) = 0.0401 at -126 degrees C), [OsO(3)F][SbF(6)] (P2(1)/c, a = 5.4772(14) A, b = 10.115(3) A, c = 12.234(3) A, beta = 99.321(5) degrees, Z = 4, and R(1) = 0.0325 at -173 degrees C), [OsO(3)F][HF](2)[AsF(6)] (P2(1)/n, a = 5.1491(9) A, b = 8.129(2) A, c = 19.636(7) A, beta = 95.099(7) degrees, Z = 4, and R(1) = 0.0348 at -117 degrees C), and [OsO(3)F][HF][SbF(6)] (Pc, a = 5.244(4) A, b = 9.646(6) A, c = 15.269(10) A, beta = 97.154(13) degrees, Z = 4, and R(1) = 0.0558 at -133 degrees C) have shown that the OsO(3)F(+) cations exhibit strong contacts to the anions and HF solvent molecules giving rise to cyclic, dimeric structures in which the osmium atoms have coordination numbers of 6. The reaction of OsO(3)F(2) with neat SbF(5) yielded [OsO(3)F][Sb(3)F(16)], which has been characterized by (19)F NMR spectroscopy in SbF(5) and SO(2)ClF solvents and by Raman spectroscopy and single-crystal X-ray diffraction in the solid state (P4(1)m, a = 10.076(6) A, c = 7.585(8) A, Z = 2, and R(1) = 0.0858 at -113 degrees C). The weak fluoride ion basicity of the Sb(3)F(16)(-) anion resulted in an OsO(3)F(+) cation (C(3)(v) point symmetry) that is well isolated from the anion and in which the osmium is four-coordinate. The geometrical parameters and vibrational frequencies of OsO(3)F(+), ReO(3)F, mu-F(OsO(3)F)(2)(+), (FO(3)Os--FPnF(5))(2), and (FO(3)Os--(HF)(2)--FPnF(5))(2) (Pn = As, Sb) have been calculated using density functional theory methods.

Syntheses and Structures of TcOF5and the Tc2O2F9+Cation and Formation of the TcOF4+Cation in Solution

The last member of the series of technetium(VII) oxide fluorides, TcOF5, has been prepared by oxidative fluorination of TcO2F3 with KrF2 in anhydrous HF. The pseudooctahedral (C4v) structure of TcOF5 has been determined by 19F and 99Tc NMR, Raman, and infrared spectroscopies and by single-crystal X-ray diffraction. TcOF5 crystallizes in the orthorhombic crystal system, space group Pna21, with a = 9.235(3) Å, b = 4.939(2) Å, c = 8.502(3) Å, V = 387.7(2) Å3, and Z = 4 at −102 °C, R1 = 0.0256 and wR2 = 0.0730. TcOF5 behaves as a fluoride ion donor toward AsF5 and SbF5 in HF solvent, giving the Tc2O2F9+ cation, which has been characterized as the AsF6- and Sb2F11- salts by Raman spectroscopy and as the [Tc2O2F9][Sb2F11] salt by single-crystal X-ray diffraction. [Tc2O2F9][Sb2F11] crystallizes in the orthorhombic crystal system, space group Pbcm, with a = 6.2925(4) Å, b = 21.205(2) Å, c = 11.7040(8) Å, V = 1561.7(2) Å3, and Z = 8 at −90 °C, R1 = 0.0368 and wR2 = 0.0896. The Tc2O2F9+ cation consists of two fluorine-bridged square pyramidal TcOF4 groups in which the fluorine bridge is trans to the oxygens. Solution 19F and 99Tc NMR spectra of Tc2O2F9+ salts in HF and of TcOF5 dissolved in SbF5 are consistent with the formation of the TcOF4+ cation. Local density functional theory has been used to calculate the geometrical parameters, vibrational frequencies, and 19F and 99Tc NMR parameters of MOF5 (M = Tc, Re, Os) and Tc2O2F9+, which are in good agreement with available experimental values. The results of ab initio calculations and normal coordinate analyses for MOF5 confirm the trans influence of oxygen, which leads to lengthening of the axial fluorine−metal bond length and a correspondingly lower stretching force constant relative to that of the shorter equatorial metal−fluorine bonds.

Fluoride ion donor properties of TcO2F3 and ReO2F3: X-ray crystal structures of MO2F3.SbF5 (M = Tc, Re) and TcO2F3.XeO2F2 and Raman and NMR spectroscopic characterization of MO2F3.PnF5 (Pn = As, Sb), [ReO2F2(CH3CN)2][SbF6], and [Re2O4F5][Sb2F11

The fluoride ion donor properties of TcO2F3 and ReO2F3 toward AsF5, SbF5, and XeO2F2 have been investigated, leading to the formation of TcO2F3.PnF5 and ReO2F3.PnF5 (Pn = As, Sb) and TcO2F3.XeO2F2, which were characterized in the solid state by Raman spectroscopy and X-ray crystallography. TcO2F3.SbF5 crystallizes in the monoclinic system P2(1)/n, with a = 7.366(2) A, b = 10.441(2) A, c = 9.398(2) A, beta = 93.32(3) degrees, V = 721.6(3) A3, and Z = 4 at 24 degrees C, R1 = 0.0649, and wR2 = 0.1112. ReO2F3.SbF5 crystallizes in the monoclinic system P2(1)/c, with a = 5.479(1) A, b = 10.040(2) A, c = 12.426(2) A, beta = 99.01(3) degrees, V = 675.1(2) A3, and Z = 4 at -50 degrees C, R1 = 0.0533, and wR2 = 0.1158. TcO2F3.XeO2F2 crystallizes in the orthorhombic system Cmc2(1), with a = 7.895(2) A, b = 16.204(3) A, c = 5.198(1) A, beta = 90 degrees, V = 665.0(2) A3, and Z = 4 at 24 degrees C, R1 = 0.0402, and wR2 = 0.0822. The structures of TcO2F3.SbF5 and ReO2F3.SbF5 consist of infinite chains of alternating MO2F4 and SbF6 units in which the bridging fluorine atoms on the antimony are trans to each other. The structure of TcO2F3.XeO2F2 comprises two distinct fluorine-bridged chains, one of TcO2F3 and the other of XeO2F2 bridged by long Tc-F...Xe contacts. The oxygen atoms of the group 7 metals in the three structures are cis to each other and to two terminal fluorine atoms and trans to the bridging fluorine atoms. The 19F NMR and Raman spectra of TcO2F3.PnF5 and ReO2F3.PnF5 in SbF5 and PnF5-acidified HF solvents are consistent with dissociation of the adducts into cis-MO2F2(HF)2+ cations and PnF6- anions. The energy-minimized geometries of the free MO2F2+ cations and their HF adducts, cis-MO2F2(HF)2+, have been calculated by local density functional theory (LDFT), and the calculated vibrational frequencies have been used as an aid in the assignment of the Raman spectra of the solid MO2F3.PnF5 adducts and their PnF5-acidified HF solutions. In contrast, ReO2F3.SbF5 ionizes in SO2ClF solvent to give the novel Re2O4F5+ cation and Sb2F11- anion. The 19F NMR spectrum of the cation is consistent with two ReO2F2 units joined by a fluorine bridge in which the oxygen atoms are assumed to lie in the equatorial plane. The [ReO2F2(CH3CN)2][SbF6] salt was formed upon dissolution of ReO2F3.SbF5 in CH3CN and was characterized by 1H, 13C, and 19F NMR and Raman spectroscopies. The ReO2F2(CH3CN)2+ cation is a pseudooctahedral cis-dioxo arrangement in which the CH3CN ligands are trans to the oxygens and the fluorines are trans to each other.

Reactions involving fluoride ion. Part 37. ‘Proton Sponge’ hydrofluoride as a fluoride ion donor

‘Proton Sponge’ hydrofluoride has been prepared and is totally soluble in acetonitrile; this system has been used to generate carbanions from hexafluoropropene and to form carbon-fluorine bonds by reaction with both 2,4,6-trichloropyrimidine and benzoyl chloride.

Structural characterization of hypervalent fluoride and oxofluoride derivatives of xenon and tellurium and iodine

The study of fluoro- and oxofluoro-anions and cations having coordination numbers higher than six has been of particular interest and is exemplified by the fluoride ion donor and electron pair acceptor properties of the oxofluorides of xenon. The X-ray crystal structure of XeOF 3 +SbF 6 − has been determined. The XeOF 3 + cation is shown to have two fluorine bridges to neighboring SbF 6 − anions, resulting in an AX 6E VSEPR arrangement around xenon in the solid state. The solution 17O NMR spectrum along with the 17O/ 18O isotope shift ratio in the 129Xe spectrum of the XeOF 3 + cation have also been obtained. The fluoride ion donor properties of XeOF 2 and the formation of the XeOF + cation are also discussed. The electron pair acceptor properties of XeOF 4, XeOF 2 and XeO 3 in the presence of nitrogen bases have been investigated by NMR spectroscopy. The XeOF 4·CH 3CN adduct has been isolated as a crystalline solid and its structure also appears to be best represented as a distorted octahedral (AX 6E) arrangement. In collaboration with Dr. K.O. Christe and Dr. W.W. Wilson (Rockwell International), a number of hypervalent anions having coordination numbers exceeding six have been prepared and characterized. The IOF 6 − anion has been characterized as its N(CH 3) 4 + salt by X-ray crystallography, vibrational spectroscopy and in solution by NMR spectroscopy. The X-ray structure shows that the anion is distorted from C 5v point symmetry by means of a puckering of the five fluorines in its equatorial plane. The structures of the N(CH 3) 4 + salts of the TeOF 6 2−, XeOF 5 −, XeF 7 − and TeF 7 − anions will also be described. The Lewis acid properties of XeF + and XeOTeF 5 + have been investigated in the presence of the nitrogen base F 5TeNH 2. The novel XeN bonded F 5TeN(H)Xe + and F 5TeN(H)XeNCH + cations have been synthesized in anhydrous HF and characterized by 1H, 15N, 19F, 125Te and 129Xe NMR spectroscopy.

Trifluoro-dithiatriazine

The missing link in the series (FCN) n(FSN) 3−n(n=O−3), the dithiatriazine (FCN)(FSN) 2, was prepared from the novel trichloride (CICN)(CISN) 2 (1) and AgF 2: ▪ Thiatriazines act as well as fluoride ion donors as acceptors, e.g. ▪ TAS + F - destroys the triathiatriazine ring system of (NSF) 3, AsF 5 reacts with (FCN) 3 to give a stable, nitrogen-bonded adduct. The new compounds were characterized by NMR- and IR-spectroscopy. The structures and bonding in these systems will be discussed.

Contributions to hydrogen-fluoride crystal chemistry

A series of systems in which hydrogen fluoride is combined with another potential proton or fluoride-ion donor or acceptor have been studied in this laboratory [1] with regard to the formation and characterization of crystalline adducts at ambient or sufficiently reduced temperatures. The main experimental methods employed are difference thermal analysis and X-ray powder diffraction for investigating the respective melting diagrams, as well as single-crystal growth and diffractometry for structure determination. Most of the adducts obtained so far are ionic with the HF component present as complex anions [H n−1F n] −. Others were found to contain fluoronium cations [H n+1F n] +. The anions and cations, with n up to eight and six, respectively, are formed by very strong FHF hydrogen bonds. Their structures will be surveyed. There are also a few adducts which are molecular, i.e. contain the HF as neutral species only. The work was supported by the Minister für Wissenschaft und Forschung des Landes Nordrhein-Westfalen, the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.

Synthesis, physical characterisation and chemical properties of methylsulphur trifluoride, CH3SF3

Methylsulphur trifluoride, CH3SF3, has been synthesised by the reaction between AgF2 and a solution of CH3SCl in CCl3F. It is a clear, viscous liquid which attacks glass, is hydrolysed rapidly, and decomposes at ambient temperatures to give CH2FSF3 and CH2FSSCH2F. The compound has been characterised by its 1H and 19F NMR and vibrational spectra, and a partial vibrational assignment is proposed. The chemistry of CH3SF3 is akin to that of SF4. Thus, it functions as a fluoride ion donor much more readily than as a fluoride ion acceptor. It reacts with Pyrex glass to give CH3S(O)F, is hydrolysed to CH3S(O)OH, and effects O–F exchange with acetone to yield 2,2-difluoropropane.