The nature of superacid electrophilic species in HF/SbF(5): a density functional theory study

A density functional theory study at the B3LYP/6-31++G** + RECP(Sb) level of the HF/SbF(5) superacid system was carried out. The geometries of possible electrophilic species, such as H(2)F(+).Sb(2)F(11)(-) and H(3)F(2)(+).Sb(2)F(11)(-), were calculated and correspond with available experimental results. Calculations of different equilibrium reactions involving HF and SbF(5) allowed the relative concentration of the most energetically favorable species present in 1:1 HF/SbF(5) solutions to be estimated. These species are H(+).Sb(2)F(11)(-), H(2)F(+).Sb(2)F(11)(-), H(3)F(2)(+).Sb(2)F(11)(-), and H(4)F(3)(+).Sb(2)F(11)(-), which correspond to 36.9, 16.8, 36.9, and 9.4%, respectively. Calculations of the acid strength of the electrophilic species were also performed and indicated that, for the same anion, the acid strength increases with the solvation degree. The entropic term also plays a significant role in proton-transfer reactions in superacid systems.     

Superelectrophilic tetrakis(carbonyl)palladium(II)- and -platinum(II) undecafluorodiantimonate(V), [Pd(CO)4][Sb(2)F(11)]2 and [Pt(CO)4][Sb(2)F(11)]2: syntheses, physical and spectroscopic properties, their crystal, molecular, and extended structures, and density functional calculations: an experimental, computational, and comparative study .

The salts [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, are prepared by reductive carbonylation of Pd[Pd(SO(3)F)(6)], Pt(SO(3)F)(4) or PtF(6) in liquid SbF(5), or HF-SbF(5). The resulting moisture-sensitive, colorless solids are thermally stable up to 140 degrees C (M = Pd) or 200 degrees C (M = Pt). Their thermal decompositions are studied by differential scanning calorimetry (DSC). Single crystals of both salts are suitable for an X-ray diffraction study at 180 K. Both isostructural salts crystallize in the monoclinic space group P2(1)/c (No. 14). The unit cell volume of [Pt(CO)(4)][Sb(2)F(11)](2) is smaller than that of [Pd(CO)(4)][Sb(2)F(11)](2) by about 0.4%. The cations [M(CO)(4)](2+), M = Pd, Pt, are square planar with only very slight angular and out-of-plane deviations from D(4)(h)() symmetry. The interatomic distances and bond angles for both cations are essentially identical. The [Sb(2)F(11)](-) anions in [M(CO)(4)][Sb(2)F(11)](2,) M = Pd, Pt, are not symmetry-related, and both pairs differ in their Sb-F-Sb bridge angles and their dihedral angles. There are in each salt four to five secondary interionic C- -F contacts per CO group. Of these, two contacts per CO group are significantly shorter than the sum of the van der Waals radii by 0.58 - 0.37 A. In addition, structural, and spectroscopic details of recently synthesized [Rh(CO)(4)][Al(2)Cl(7)] are reported. The cations [Rh(CO)(4)](+) and [M(CO)(4)](2+), M = Pd, Pt, are characterized by IR and Raman spectroscopy. Of the 16 vibrational modes (13 observable, 3 inactive) 10 (Pd, Pt) or 9 (Rh), respectively, are found experimentally. The vibrational assignments are supported by DFT calculations, which provide in addition to band positions also intensities of IR bands and Raman signals as well as internal force constants for the cations. (13)C NMR measurements complete the characterization of the square planar metal carbonyl cations. The extensive characterization of [M(CO)(4)][Sb(2)F(11)](2), M = Pd, Pt, reported here, allows a comparison to linear and octahedral [M(CO)(n)()][Sb(2)F(11)](2) salts [M = Hg (n = 2); Fe, Ru, Os (n = 6)] and their derivatives, which permit a deeper understanding of M-CO bonding in the solid state for superelectrophilic cations with [Sb(2)F(11)](-) or [SbF(6)](-) as anions.     

Synthesis and characterization of the first examples of perfluoroalkyl-substituted trialkyloxonium salts, [(CH3)2OCF3]+[Sb2F11]- and [(CH3)2OCF(CF3)2]+[Sb2F11]-

In the superacidic HF/SbF(5) system, methyl trifluoromethyl ether forms at -78 degrees C the new tertiary oxonium salt [(CH(3))(2)OCF(3)](+)[Sb(2)F(11)](-), which was characterized by Raman and multinuclear NMR spectroscopy and its crystal structure. The same oxonium salt was also obtained by methylation of CH(3)OCF(3) with CH(3)F and SbF(5) in HF solution at -30 to -10 degrees C. Replacement of one methyl group in the trimethyloxonium cation by the bulkier and more electronegative trifluoromethyl group increases the remaining O-CH(3) bond lengths by 0.037(1) A and the sum of the C-O-C bond angles by about 4.5 degrees. Methylation of CH(3)OCF(CF(3))(2) with CH(3)F in HF/SbF(5) solution at -30 degrees C produces [(CH(3))(2)OCF(CF(3))(2)](+)[Sb(2)F(11)](-). The observed structure and vibrational and NMR spectra were confirmed by theoretical studies at the B3LYP/6-311++G(2d,2p) and the MP2/6-311++G(2d,p) levels.     

The Osmium(VIII) Oxofluoro Cations OsO(2)F(3)(+) and F(cis-OsO(2)F(3))(2)(+): Syntheses, Characterization by (19)F NMR Spectroscopy and Raman Spectroscopy, X-ray Crystal Structure of F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-), and Density Functional Theory Calculations of OsO(2)F(3)(+), ReO(2)F(3), and F(cis-OsO(2)F(3))(2)(+)

Osmium dioxide tetrafluoride, cis-OsO(2)F(4), reacts with the strong fluoride ion acceptors AsF(5) and SbF(5) in anhydrous HF and SbF(5) solutions to form orange salts. Raman spectra are consistent with the formation of the fluorine-bridged diosmium cation F(cis-OsO(2)F(3))(2)(+), as the AsF(6)(-) and Sb(2)F(11)(-) salts, respectively. The (19)F NMR spectra of the salts in HF solution are exchange-averaged singlets occurring at higher frequency than those of the fluorine environments of cis-OsO(2)F(4). The F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-) salt crystallizes in the orthorhombic space group Imma. At -107 degrees C, a = 12.838(3) ?, b = 10.667(2) ?, c = 11.323(2) ?, V = 1550.7(8) ?(3), and Z = 4. Refinement converged with R = 0.0469 [R(w) = 0.0500]. The crystal structure consists of discrete fluorine-bridged F(cis-OsO(2)F(3))(2)(+) and Sb(2)F(11)(-) ions in which the fluorine bridge of the F(cis-OsO(2)F(3))(2)(+) cation is trans to an oxygen atom (Os-O 1.676 ?) of each OsO(2)F(3) group. The angle at the bridge is 155.2(8) degrees with a bridging Os---F(b) distance of 2.086(3) ?. Two terminal fluorine atoms (Os-F 1.821 ?) are cis to the two oxygen atoms (Os-O 1.750 ?), and two terminal fluorine atoms of the OsO(2)F(3) group are trans to one another (1.813 ?). The OsO(2)F(3)(+) cation was characterized by (19)F NMR and by Raman spectroscopy in neat SbF(5) solution but was not isolable in the solid state. The NMR and Raman spectroscopic findings are consistent with a trigonal bipyramidal cation in which the oxygen atoms and a fluorine atom occupy the equatorial plane and two fluorine atoms are in axial positions. Density functional theory calculations show that the crystallographic structure of F(cis-OsO(2)F(3))(2)(+) is the energy-minimized structure and the energy-minimized structures of the OsO(2)F(3)(+) cation and ReO(2)F(3) are trigonal bipyramidal having C(2)(v)() point symmetry. Attempts to prepare the OsOF(5)(+) cation by oxidative fluorination of cis-OsO(2)F(4) with KrF(+)AsF(6)(-) in anhydrous HF proved unsuccessful.     

Homoleptic, sigma-bonded octahedral [M(CO)(6)](2+) cations of iron(II), ruthenium(II), and osmium(II). Part 1: Syntheses, thermochemical and vibrational characterizations, and molecular structures as [Sb(2)F(11)](-) and [SbF(6)](-) salts. A comprehensive, comparative study

Homoleptic octahedral, superelectrophilic sigma-bonded metal carbonyl cations of the type [M(CO)(6)](2+) (M = Ru, Os) are generated in the Bronsted-Lewis conjugate superacid HF/SbF(5) by reductive carbonylation of M(SO(3)F)(3) (M = Ru, Os) or OsF(6). Thermally stable salts form with either [Sb(2)F(11)](-) or [SbF(6)](-) as anion, just as for the previously reported [Fe(CO)(6)](2+) cation. The latter salts are generated by oxidative (XeF(2)) carbonylation of Fe(CO)(5) in HF/SbF(5). A rationale for the two diverging synthetic approaches is provided. The thermal stabilities of [M(CO)(6)][SbF(6)](2) salts, studied by DSC, range from 180 degrees C for M = Fe to 350 degrees C for M = Os before decarbonylation occurs. The two triads [M(CO)(6)][SbF(6)](2) and [M(CO)(6)][Sb(2)F(11)](2) (M = Fe, Ru, Os) are extensively characterized by single-crystal X-ray diffraction and vibrational and (13)C NMR spectroscopy, aided by computational studies of the cations. The three [M(CO)(6)][SbF(6)](2) salts (M = Fe, Ru, Os) crystallize in the tetragonal space group P4/mnc (No. 128), whereas the corresponding [Sb(2)F(11)](-) salts are monoclinic, crystallizing in space group P2(1)/n (No. 14). In both triads, the unit cell parameters are nearly invariant of the metal. Bond parameters for the anions [SbF(6)](-) and [Sb(2)F(11)](-) and their vibrational properties in the two triads are completely identical. In all six salts, the structural and vibrational properties of the [M(CO)(6)](2+) cations (M = Fe, Ru, Os) are independent of the counteranion and for the most part independent of M and nearly identical. Interionic C...F contacts are similarly weak in all six salts. Metal dependency is noted only in the (13)C NMR spectra, in the skeletal M-C vibrations, and to a much smaller extent in some of the C-O stretching fundamentals (A(1g) and T(1u)). The findings reported here are unprecedented among metal carbonyl cations and their salts.     

Behavior of BrO3F and ClO3F toward strong Lewis acids and the characterization of [XO2][SbF6] (X = Cl, Br) by single crystal X-ray diffraction, Raman spectroscopy, and computational methods

The interactions of BrO3F and ClO3F with the strong Lewis acids AsF5 and SbF5 were investigated. Although ClO3F is unreactive toward AsF5 and SbF5, BrO3F undergoes fluoride ion abstraction and O2 elimination, accompanied by central halogen reduction, to form [BrO2][Sb(n)F(5n+1)] (n > or = 1), rather than simple fluoride ion abstraction to form BrO3(+) salts. The geometric parameters of the BrO2(+) cation have been obtained in the solid state for the first time by a single-crystal X-ray diffraction study of [BrO2][SbF6] at -173 degrees C and are compared with those of ClO2(+) salts. Quantum-chemical calculations have been used to arrive at the geometries and vibrational frequencies of XO2(+) and XO3(+) (X = Cl, Br) and have been compared with the experimental values for XO2(+). The calculations have also been used to account for the contrasting behaviors of ClO3F and BrO3F toward central halogen reduction in the presence of liquid SbF5. The thermochemical stabilities of ClO3(+) and BrO3(+) salts of the AsF6(-), SbF6(-), Sb2F11(-), and Sb3F16(-) were also investigated, which provided the fluoride ion affinities of AsF5, SbF5, Sb2F10, and Sb3F15 up to and including the CCSD(T) level of theory. These values are compared with the current literature values. Thermochemical studies indicate that XO3(+) formation by fluoride ion abstraction from XO3F is not spontaneous under standard conditions whereas a concerted fluoride abstraction and O2 elimination to give the XO2(+) cations is spontaneous to near thermally neutral. Failure to observe reactivity between ClO3F and any of the aforementioned Lewis acid fluoride ion acceptors is attributed to a significant kinetic barrier to fluoride ion abstraction.     

CF3 oxonium salts, O-(trifluoromethyl)dibenzofuranium salts: in situ synthesis, properties, and application as a real CF3+ species reagent

We report in situ synthesis of the first CF(3) oxonium salts, thermally unstable O-(trifluoromethyl)dibenzofuranium salts, which furthermore have different counteranions (BF(4)-, PF(6)-, SbF(6)-, and Sb(2)F(11)-) and ring substituents (tert-butyl, F, and OCH(3)), by photochemical decomposition of the corresponding 2-(trifluoromethoxy)biphenylyl-2'-diazonium salts at -90 to -100 degrees C. The yields markedly increased in the order of BF(4)- < PF(6)- < SbF(6)- < Sb(2)F(11)-. The CF(3) oxonium salts were fully assigned by means of (1)H and (19)F NMR spectroscopy at low temperature. The CF(3) salts decomposed to form CF(4) and dibenzofurans. The half-life times at -60 degrees C of the 2-tert-butyl salts having different counteranions were 29 min for BF(4)- salt 2d, 36 min for PF(6)- salt 2c, 270 min for SbF(6)- salt 2a, and 415 min for Sb(2)F(11)- salt 2b. Those at -60 degrees C of the Sb(2)F(11)- salts having different 2-substituents were 13 min for F salt 3b, 63 min for H (unsubstituted) salt 1b, and 415 min for tert-butyl salt 2b. Thus, the stability of the CF(3) oxonium salts increased in the order of BF(4)- < PF(6)- < SbF(6)- < Sb(2)F(11)- and F < H < tert-butyl, which is in accord with the increasing orders of the non-nucleophilicity of counteranions and the electron-donating effect of ring substituents. 2-tert-Butyl-O-(trifluoromethyl)dibenzofuranium hexafluoroantimonate (2a) was thus chosen and successfully applied as a real CF(3)+ species source to the direct O- and N-trifluoromethylations of alcohols, phenols, amines, anilines, and pyridines under very mild conditions. The thermal decomposition method with a mixture of diazonium salt 17a and aryl- or alkylsulfonic acids, pyridine, or pyridines having an electron-withdrawing group also afforded CF(3)O or CF(3)N products. The trifluoromethylation mechanism is discussed and an S(N)2 mechanism containing the transient formation of free CF(3)+ is proposed. Thus, the present study has demonstrated that the exceedingly reactive CF(3)+ species can be generated much easier than the CH(3)+ species, contrary to the common sense that CF(3)+ is extremely difficult to generate in solution.     

Syntheses and X-ray crystal structures of alpha- and beta-[XeO2F][SbF6], [XeO2F][AsF6], [FO2XeFXeO2F][AsF6], and [XeF5][SbF6)].XeOF4 and computational studies of the XeO2F+ and FO2XeFXeO2F+ cations and related species

Reactions of XeO2F2 with the strong fluoride ion acceptors, AsF5 and SbF5, in anhydrous HF solvent give rise to alpha- and beta-[XeO2F][SbF6], [XeO2F][AsF6], and [FO2XeFXeO2F][AsF6]. The crystal structures of alpha-[XeO2F][SbF6] and [XeO2F][AsF6] consist of trigonal-pyramidal XeO2F+ cations, which are consistent with an AXY2E VSEPR arrangement, and distorted octahedral MF6- (M = As, Sb) anions. The beta-phase of [XeO2F][SbF6] is a tetramer in which the xenon atoms of four XeO2F+ cations and the antimony atoms of four SbF6- anions are positioned at alternate corners of a cube. The FO2XeFXeO2F+ cations of [FO(2)XeFXeO2F][AsF6] are comprised of two XeO2F units that are bridged by a fluorine atom, providing a bent Xe- - -F- - -Xe arrangement. The angle subtended by the bridging fluorine atom, a xenon atom, and the terminal fluorine atom of the XeO2F group is bent toward the valence electron lone-pair domain on xenon, so that each F- - -XeO2F moiety resembles the AX(2)Y(2)E arrangement and geometry of the parent XeO2F2 molecule. Reaction of XeF6 with [H3O][SbF6] in a 1:2 molar ratio in anhydrous HF predominantly yielded [XeF5][SbF6].XeOF4 as well as [XeO2F][Sb2F11]. The crystal structure of the former salt was also determined. The energy-minimized, gas-phase MP2 geometries for the XeO2F+ and FO2XeFXeO2F+ cations are compared with the experimental and calculated geometries of the related species IO2F, TeO2F-, XeO2(OTeF5)+, XeO2F2, and XeO2(OTeF5)2. The bonding in these species has been described by natural bond orbital and electron localization function analyses. The standard enthalpies and Gibbs free energies for reactions leading to XeO2F+ and FO2XeFXeO2F+ salts from MF5 (M = As, Sb) and XeO2F2 were obtained from Born-Haber cycles and are mildly exothermic and positive, respectively. When the reactions are carried out in anhydrous HF at low temperatures, the salts are readily formed and crystallized from the reaction medium. With the exception of [XeO2F][AsF6], the XeO2F+ and FO2XeFXeO2F+ salts are kinetically stable toward dissociation to XeO2F2 and MF5 at room temperature. The salt, [XeO2F][AsF6], readily dissociates to [FO2XeFXeO2F][AsF6] and AsF5 under dynamic vacuum at 0 degree C. The decompositions of XeO2F+ salts to the corresponding XeF+ salts and O2 are exothermic and spontaneous but slow at room temperature.     

Polynitrogen chemistry: preparation and characterization of (N5)2SnF6, N5SnF5, and N5B(CF3)4

Metathetical processes were used to convert N5SbF6 into N5[B(CF3)4] and (N5)2SnF6. The latter salt is especially noteworthy because it contains two N5+ ions per anion, thus demonstrating that salts with touching polynitrogen cations can be prepared. This constitutes an important milestone towards our ultimate goal of synthesizing a stable, ionic nitrogen allotrope. The stepwise decomposition of (N5)2SnF6 yielded N5SnF5. Multinuclear NMR spectra show that in HF the SnF5- ion exists as a mixture of Sn2F(10)(2-) and Sn4F(20)(4-) ions. Attempts to isolate FN5 from the thermolysis of (N5)2SnF6 were unsuccessful, yielding only the expected decomposition products, FN3, N2, trans-N2F2, NF3, and N2.     

Structures of the BrF(4)(+) and IF(4)(+) cations

The large discrepancies between the calculated and observed structures for BrF(4)(+) and IF(4)(+) (Christe, K. O.; Zhang, X.; Sheehy, J. A.; Bau, R. J. Am. Chem. Soc. 2001, 123, 6338) prompted a redetermination of the crystal structures of BrF(4)(+)Sb(2)F(11)(-) (monoclinic, P2(1)/c, a = 5.2289(6) A, b = 14.510(2) A, c = 14.194(2) A, beta = 90.280(1) degrees, Z = 4) and IF(4)(+)SbF(6)(-) (orthorhombic, Ibca, a = 8.2702(9) A, b = 8.3115(9) A, c = 20.607(2) A, Z = 8). It is shown that for BrF(4)(+), the large differences were mainly due to large errors in the original experimental data. For IF(4)(+)SbF(6)(-), the geometry previously reported for IF(4)(+) was reasonably close to that found in this study despite a very large R-factor of 0.15 and a refinement in an incorrect space group. The general agreement between the calculated and the redetermined geometries of BrF(4)(+) and IF(4)(+) is excellent, except for the preferential compression of one bond angle in each ion due to the influence of interionic fluorine bridges. In BrF(4)(+), the fluorine bridges are equatorial and compress this angle. In IF(4)(+), the nature of the fluorine bridges depends on the counterion, and either the axial (in IF(4)(+)SbF(6)(-)) or the equatorial (in IF(4)(+)Sb(2)F(11)(-)) bond angle is preferentially compressed. Therefore, the geometries of the free ions are best described by the theoretical calculations.     

Crystal structures and spectroscopic characterization of radical cations and dications of oligothiophenes stabilized by annelation with bicyclo[2.2.2]octene units: sterically segregated cationic oligothiophenes

The remarkably stable SbF(6)(-) salts of the radical cations of bithiophene 1(2T) and terthiophene 1(3T), completely surrounded by bicyclo[2.2.2]octene (BCO) units, were obtained by one-electron oxidation of the neutral precursors with NO(+)SbF(6)(-), and their solid-state structures were determined by X-ray crystallography. In these radical cations, the presence of quinoidal character was apparent, as shown by the increased planarity and by comparison of the bond lengths with those of the neutral precursors. The shortest intermolecular pi-pi distances in the crystal structure of 1(2T)(*)(+)SbF(6)(-) (distance between two sp(2) carbon atoms, 4.89 A) and 1(3T)(*)(+)SbF(6)(-) (distance between an sp(2) carbon and a sulfur atom, 3.58 A) were found to be longer than the sums of the van der Waals radii of the corresponding atoms. In accord with this, no apparent change was observed in ESR and UV-vis-NIR spectra of solutions of 1(2T)(*)(+) and 1(3T)(*)(+) upon lowering the temperature, indicating that the pi- (or sigma-) dimer formation is inhibited in solution as well as in the solid state. The dications 1(2T)(2+) and 1(3T)(2+) were generated with the stronger oxidant SbF(5) in CH(2)Cl(2) at -40 degrees C and characterized by NMR spectroscopy. In the (1)H NMR spectra, two conformers were observed for each dication of both 1(2T)(2+) (transoid (t) and cisoid (c)) and 1(3T)(2+) (t,t and c,t) at room temperature due to the high rotational barrier around the inter-ring bond(s) between thiophene rings, which was caused by the enhanced double bond character of these bonds following two-electron oxidation. This is supported by DFT calculations (B3LYP/6-31G(d)), which predicted the rotational barriers in the dications of unsubstituted bithiophene and terthiophene to be 27.6 and 22.9 kcal mol(-)(1), respectively. In the case of quaterthiophene and sexithiophene surrounded by BCO frameworks 1(4T) and 1(6T), oxidation with even one molar equivalent of NO(+)SbF(6)(-) afforded the dication salts 1(4T)(2+)2SbF(6)(-) and 1(6T)(2+)2SbF(6)(-), which were isolated as stable single crystals and allowed the X-ray crystallography. In their crystal structures, the cationic pi-systems became planar again due to the great contribution of quinoidal resonance structures, and the pi-systems, which were arrayed in a parallel geometry, were also segregated by the steric effect of BCO units. The degree and tendency of changes in the bond lengths of thiophene rings of 1(4T)(2+) and 1(6T)(2+) as compared with neutral precursors were similar to those of 1(2T)(*)(+)SbF(6)(-) and 1(3T)(*)(+)SbF(6)(-), respectively, implying that the contribution of quinoidal character is modulated by the amount of positive charge per thiophene unit.     

The synthesis,vibrational spectra,and molecular structure of [Ir(CO)(6)][SbF(6)](3).4HF - the first structurally characterized salt with a tripositive,homoleptic metal carbonyl cation and the first example of a tetrahedral hydrogen-bonded (HF)(4) cluster

The reductive carbonylation of IrF(6) in a dilute solution of SbF(5) in anhydrous HF (1:6 by volume) produces surprisingly at 25 degrees C and 1.5 atm CO the complex salt [Ir(CO)(6)][SbF(6)](3).4HF, while [Ir(CO)(6)][Sb(2)F(11)](3) is obtained in liquid SbF(5) under similar conditions. Vibrational spectra in the CO stretching range for both salts and [Ir(CO)(6)](3+)((solv)) are identical within error limits, and nu(CO)(av) is with 2269 cm(-1) the highest average stretching frequency so far observed for octahedral metal carbonyl cations. A vibrational assignment supported by DFT calculations is presented, and the vibrational fundamentals are compared to those of [Os(CO)(6)](2+). The molecular structure of [Ir(CO)(6)][SbF(6)](3).4HF is determined by single-crystal X-ray diffraction. Crystal data for [Ir(CO)(6)][SbF(6)](3).4HF: rhombohedral, R3c (No. 161), a = 14.630(4) A, c = 18.377(7) A, V = 3406.4(18) A(3), Z = 6, T = 150 K, R(1) = 0.0338 [I > 2sigma (I)], wR(2) = 0.0797). The average Ir-C bond length in the octahedral [Ir(CO)(6)](3+) cation is with 2.029(10) the longest observed for iridium carbonyl derivatives, consistent with the absence of Ir --> CO pi-back-bonding. The four solvate HF molecules form a tetrahedron via long, asymmetric, and partly delocalized hydrogen bonds with F-F edge lengths of 2.857 (3x) and 2.914 (3x) A. There is no precedent for a polyhedral (HF)(n) cluster in the gas, liquid, or solid phase. The four F atoms of the (HF)(4) cluster are coordinated to the C atoms of the six CO ligands of the cation, which again is without precedent. The coordination of one of the F atoms to three C atoms in a iso-tridentate mode with contact distances C-F(8) of 2.641(10) A is most unusual. The observed tight C-F coordination in [Ir(CO)(6)][SbF(6)](3).4HF provides conclusive evidence for the presence of electrophilic carbon in the cation and illustrates how superelectrophilic cations such as [Ir(CO)(6)](3+) are solvent stabilized in the conjugate Br?nsted-Lewis superacid HF-SbF(5).     

Structures of Sb(OC(6)H(3)Me(2)-2,6)(3) and Sb(OEt)(5) x NH(3): the first authenticated monomeric Sb(OR)(n) (n = 3, 5)

The first monomeric antimony alkoxides, Sb(OC(6)H(3)Me(2))(3) (1) and Sb(OEt)(5) x NH(3) (2), have been crystallographically characterized. The former adopts a trigonal pyramidal geometry, while the latter is octahedral about antimony; hydrogen bonding between NH(3) and SbOEt groups in Sb(OEt)(5) small middle dotNH(3) creates a one-dimensional lattice arrangement. Reaction of pyridine with SbCl(5) in EtOH/hexane yields the salt [Hpy(+)](9)[Sb(2)Cl(11)(5)(-)][Cl(-)](4) (3), which has also been crystallographically characterized. Crystallographic data: 1, C(24)H(27)O(3)Sb, a = 10.9080(2), b = 11.9660(2), c = 17.7260(4) A, alpha = 109.740(1) degrees, monoclinic P2(1)/c (unique axis a), Z = 4; 2, C(10)H(28)NO(5)Sb, a = 7.7220(1), b = 19.0700(2), c = 21.6800(3) A, beta = 93.4960(7) degrees, monoclinic P2(1)/c, Z = 8; 3, C(45)H(54)Cl(15)N(9)Sb(2), a = 13.4300(2), b = 14.4180(2), c = 17.4180(3) A, alpha = 82.7650(7), beta = 77.5570(7), gamma = 70.7670(7) degrees, triclinic P1, Z = 2.     

Syntheses and structures of Ag(I)-containing coordination polymers and Co(II)-containing supramolecular complex based on novel fulvene ligands

Three new rigid conjugated fulvene ligands L1-L3 were synthesized. L1 and L3 have been prepared by an aroylation reaction of cyclohexyl-substituted cyclopentadienyl anions. L2 was prepared by the reaction of L1 with PhNHNH2 in hot enthanol. Six new coordination polymers, namely [Ag(C25H20N2O2)(ClO4)] x 3.5C6H6 (1), [Ag2(mu-C31H24N4)(eta2-C6H6)(H2O)](ClO4)2 x (C6H6) x (H2O)0.5 (3), [Ag(C31H24N4)]SbF6 x solvate (4), [Ag(C31H24N4)](SbF6)2 x 2C6H6 x CH2Cl2 (5), [Ag(C25H20N2O2)2]SbF6 (6), and [Ag(C25H20N2O2)2]SbF6 (7), and one seven-membered cobaltacycle-containing complex, namely Co(C25H20N2O2)2(C2H5OH)2 (2), were obtained through self-assembly based on these three new fulvene lignads. L2-L3 and compounds 1-7 have been fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The results indicate that the coordination chemistry of new fulvene ligands is versatile. They can bind metal ions not only through the terminal N-donors and fulvene carbon atoms into organometallic coordination polymers but also through the two chelating carbonyl groups into unusual seven-membered metallo-ring supramolecular complexes. In the solid state, ligands L1-L3 are luminescent. A blue-shift in the emission was observed between the free ligand L1 and the one incorporated into Co(II)-containing complex 2, and a red-shift in the emission was observed between the free ligand L3 and the one incorporated into Ag(I)-containing polymeric compounds 6 and 7.     

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.     

Cationic carbonyl complexes of rhodium(I) and rhodium(III): syntheses,vibrational spectra,NMR studies,and molecular structures of tetrakis(carbonyl)rhodium(I) heptachlorodialuminate and -gallate, [Rh(CO)4][Al2Cl7] and [Rh(CO)4][Ga2Cl7

Dimeric rhodium(I) bis(carbonyl) chloride, [Rh(CO)(2)(mu-Cl)](2), is found to be a useful and convenient starting material for the syntheses of new cationic carbonyl complexes of both rhodium(I) and rhodium(III). Its reaction with the Lewis acids AlCl(3) or GaCl(3) produces in a CO atmosphere at room temperature the salts [Rh(CO)(4)][M(2)Cl(7)] (M = Al, Ga), which are characterized by Raman spectroscopy and single-crystal X-ray diffraction. Crystal data for [Rh(CO)(4)][Al(2)Cl(7)]: triclinic, space group Ponemacr; (No. 2); a = 9.705(3), b = 9.800(2), c = 10.268(2) A; alpha = 76.52(2), beta = 76.05(2), gamma = 66.15(2) degrees; V = 856.7(5) A(3); Z = 2; T = 293 K; R(1) [I > 2sigma(I)] = 0.0524, wR(2) = 0.1586. Crystal data for [Rh(CO)(4)][Ga(2)Cl(7)]: triclinic, space group Ponemacr; (No. 2); a = 9.649(1), b = 9.624(1), c = 10.133(1) A; alpha = 77.38(1), beta = 76.13(1), gamma = 65.61(1) degrees; V = 824.4(2) A(3); Z = 2; T = 143 K; R(1) [I > 2sigma(I)] = 0.0358, wR(2) = 0.0792. Structural parameters for the square planar cation [Rh(CO)(4)](+) are compared to those of isoelectronic [Pd(CO)(4)](2+) and of [Pt(CO)(4)](2+). Dissolution of [Rh(CO)(2)Cl](2) in HSO(3)F in a CO atmosphere allows formation of [Rh(CO)(4)](+)((solv)). Oxidation of [Rh(CO)(2)Cl](2) by S(2)O(6)F(2) in HSO(3)F results in the formation of ClOSO(2)F and two seemingly oligomeric Rh(III) carbonyl fluorosulfato intermediates, which are easily reduced by CO addition to [Rh(CO)(4)](+)((solv)). Controlled oxidation of this solution with S(2)O(6)F(2) produces fac-Rh(CO)(3)(SO(3)F)(3) in about 95% yield. This Rh(III) complex can be reduced by CO at 25 degrees C in anhydrous HF to give [Rh(CO)(4)](+)((solv)); addition of SbF(5) at -40 degrees C to the resulting solution allows isolation of [Rh(CO)(4)][Sb(2)F(11)], which is found to have a highly symmetrical (D(4)(h)()) [Sb(2)F(11)](-) anion. Oxidation of [Rh(CO)(2)Cl](2) in anhydrous HF by F(2), followed in a second step by carbonylation in the presence of SbF(5), is found to be a simple, straightforward route to pure [Rh(CO)(5)Cl][Sb(2)F(11)](2), which has previously been structurally characterized by us. All new complexes are characterized by vibrational and NMR spectroscopy. Assignment of the vibrational spectra and interpretation of the structural data are supported by DFT calculations.     

Syntheses and characterization of the MF6- (M = As, Sb) salts of the simple trithietanylium PhCS3+ cation and the identity of PhCS3Cl

MF6- (M = As or Sb) salts of a simple derivative of the trithietanylium PhCSSS+, 1, were synthesized for the first time by the reaction of PhCS3Cl and AgMF6 in liquid SO2. 1SbF6 was characterized by IR, FT-Raman, and NMR spectroscopy, elemental analysis, and a preliminary X-ray crystal structure. 1AsF6 was characterized by 1H NMR and FT-Raman spectroscopy. The calculated (MPW1PW91/3-21G* or 6-31G*) geometries, 1H and 13C chemical shifts (MPW1PW91/6-311G(2DF)//MPW1PW91/3-21G*), and vibrational frequencies and intensities (MPW1PW91/6-31G*) were in satisfactory agreement with the observed values. The calculated pi type molecular orbitals of HCSSS+ (MPW1PW91/6-311+G*) and 1 (MPW1PW91/3-21G*) imply that the 6pi-CSSS+ ring has some aromatic character. 1SbF6 undergoes a metathesis reaction with NBu4Cl in liquid SO2 to give PhCS3Cl, which was characterized by vibrational spectroscopy and mass spectrometry. The evidence indicates that PhCS3Cl has the ionic formulation PhCSSS+ Cl- with significant cation-anion interactions in the solid state. ArCSSS+ SbF6- (Ar = 1-naphthyl), 14SbF6, was prepared from ArCS3Cl and AgSbF6, suggesting that the synthesis of MF6- (M = As or Sb) salts of RCSSS+ is potentially general for aryl derivatives. The structure of 14SbF6 was established by 1H and 13C NMR, IR, and FT-Raman spectroscopy, and theoretical calculations gave values in agreement with the experimental data.     

The synthesis and the molecular structure of hexakis(carbonyl)hexafluoroantimonato(V)tungsten(II) undecafluorodiantimonate(V), [W(CO)6(FSbF5)][Sb2F11

The reaction of tungsten hexacarbonyl, W(CO)6, with antimony(V) fluoride, SbF5, in the conjugate Br?nsted-Lewis superacid HF-SbF5 at 40 degrees C produces quantitatively the salt [W(CO)6(FSbF5)][Sb2F11] as the main product. The observed 2e- oxidation without any loss of CO is unprecedented. The cation [W(CO)6(FSbF5)]+ is seven coordinated with a distorted C2v capped trigonal prismatic structure. [W(CO)6(FSbF5)][Sb2F11] crystallizes in the monoclinic space group P21 (No. 4). a = 8.2051(12) A, b = 16.511(3) A, c = 8.1432(2) A, beta = 111.5967(6) degrees, V = 1025.8(2) A3, Z = 2. Number of reflections measured = 9112, unique 4410. Residuals on F, I > 3 sigma (I): R (Rw) = 0.023 (0.023). In the [W(CO)6(FSbF5)]+ cation the FSbF5 group is very tightly coordinated to tungsten with the bridging fluorine nearly equidistant from W and Sb. The details of the molecular structure are compared to those to polymeric [[Mo(CO)4]2(cis-mu-F2SbF4)3]x[Sb2F11]x reported by us very recently.     

Pentamethylcyclopentadienyl-iridium(III) complexes with pyridylamino ligands: synthesis and applications as asymmetric catalysts for Diels-Alder reactions

Reaction of the dimer [(Cp*IrCl)2(P-Cl)2] with chiral pyridylamino ligands (pyam, L1-L5) in the presence of NaSbF6 gave complexes [Cp*IrCl(pyam)][SbF6] 1-5 as diastereomeric mixtures, which have been fully characterised, including the X-ray molecular structure determination of the complexes (S(Ir),R(N),R(C))-[Cp*IrClL1][SbF6] 1a and (R(Ir),S(N),S(C))-[Cp*IrClL5][SbF6] 5a. Treatment of these cations with AgSbF6 affords the corresponding aqua species [Cp*Ir(pyam)(H2O)][SbF6]2 6-10 which have been also fully characterised. The molecular structure of the complex (S(Ir),R(N),R(C))-[Cp*IrL,(H2O)][SbF6]2 6 has been determined by X-ray diffractometric methods. The aqua complexes [Cp*Ir(pyam)(H2O)][SbF6]2 (6, pyam = L2 (7), L3 (8)) evolve to the cyclometallated species [Cp*Ir{kappa3(N,N',C)-(R)-(C6H4)CH(CH3)NHCH2C5NH4}][SbF6] (11), [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)-NHCH2C5NH4)}][SbF6] (12), and [Cp*Ir{kappa3(N,N',C)-(R)-(C10H6)CH(CH3)NHCH2C9NH6)}][SbF6] (13) respectively, via intramolecular activation of an ortho C-H aryl bond. Complexes 6-10 are enantioselective catalysts for the Diels-Alder reaction between methacrolein and cyclopentadiene. Reaction occurs rapidly at room temperature with good exo : endo selectivity (from 81 : 19 to 98 : 2) and moderate enantioselectivity (up to 72%). The involved intermediate Lewis acid-dienophile compounds [Cp*Ir(pyam)(methacrolein)][SbF]2 (pyam = L4 (14), L5 (15)) have been isolated and characterised.     

Syntheses and Vibrational and (13)C MAS-NMR Spectra of Bis(carbonyl)mercury(II) Undecafluorodiantimonate(V) ([Hg(CO)(2)][Sb(2)F(11)](2)) and of Bis(carbonyl)dimercury(I) Undecafluorodiantimonate ([Hg(2)(CO)(2)][Sb(2)F(11)](2)) and the Molecular Structure of [Hg(CO)(2)][Sb(2)F(11)](2)

The synthesis of bis(carbonyl)mercury(II) undecafluorodiantimonate(V), [Hg(CO)(2)][Sb(2)F(11)](2), and that of the corresponding mercury(I) salt [Hg(2)(CO)(2)][Sb(2)F(11)](2) are accomplished by the solvolyses of Hg(SO(3)F)(2) or of Hg(2)F(2), treated with fluorosulfuric acid, HSO(3)F, in liquid antimony(V) fluoride at 80 or 60 degrees C, respectively, in an atmosphere of CO (500-800 mbar). The resulting white solids are the first examples of metal carbonyl derivatives formed by a post-transition element. Both salts are characterized by FT-IR, FT-Raman, and (13)C-MAS-NMR spectroscopy. For [Hg(CO)(2)][Sb(2)F(11)], unprecedentedly high CO stretching frequencies (nu(av) = 2279.5 cm(-)(1)) and stretching force constant (f(r) = 21.0 +/- 0.1) x 10(2) Nm(-)(1)) are obtained. Equally unprecedented is the (1)J((13)C-(199)Hg) value of 5219 +/- 5 Hz observed in the (13)C MAS-NMR spectrum of the (13)C labeled isotopomers at delta = 168.8 +/- 0.1 ppm. The corresponding values (nu(av) = 2247 cm(-)(1), f(r) = (20.4 +/- 0.1) x 10(2) Nm(-)(1), (1)J((13)C-(199)Hg) = 3350 +/- 50 Hz and (2)J((13)C-(199)Hg) 850 +/- 50 Hz) are found for [Hg(2)(CO)(2)][Sb(2)F(11)](2), which has lower thermal stability (decomposition point in a sealed tube is 140 degrees C vs 160 degrees C for the Hg(II) compound) and a decomposition pressure of 8 Torr at 20 degrees C. The mercury(I) salt is sensitive toward oxidation to [Hg(CO)(2)][Sb(2)F(11)](2) during synthesis. Both linear cations (point group D(infinity)(h)()) are excellent examples of nonclassical (sigma-only) metal-CO bonding. Crystal data for [Hg(CO)(2)][Sb(2)F(11)](2): monoclinic, space group P2(1)/n; Z = 2; a = 7.607(2) ?; b = 14.001(3) ?; c = 9.730(2) ?; beta = 111.05(2) degrees; V = 967.1 ?(3); T = 195 K; R(F) = 0.035 for 1983 data (I(o) >/= 2.5sigma(I(o))) and 143 variables. The Hg atom lies on a crystallographic inversion center. The Hg-C-O angle is 177.7(7) degrees. The length of the mercury-carbon bond is 2.083(10) ? and of the C-O bond 1.104(12) ? respectively. The structure is stabilized in the solid state by a number of significant secondary interionic Hg- - -F and C- - -F contacts.