ABSTRACT
The rotational spectra of the fluorosulfate (FSO(3)) molecular radical in its vibronic ground state were measured in the millimeter-wave region and analyzed in detail using the matrix elements of the rotational, fine, and hyperfine Hamiltonian terms. The analysis of the assigned transition frequencies made it possible to derive very precise values of the rotational, centrifugal distortion and fine structure constants and to confirm the C(3v) molecular symmetry of the vibronic ground state unambiguously. In addition, an effective parameter of the "A(1)-A(2) splitting" was determined. The rotational transitions of the FSO(3) free radical were observed, identified, and analyzed for the first time.
ABSTRACT
A convenient one-step synthesis for [Mn(CO)6]+ salts has been developed. The method involves the one-electron oxidation of Mn2(CO)10 by protons in solutions of Lewis acids (BF3, (CF3)3BCO) and anhydrous HF. The molecular structure of [Mn(CO)6][BF4].SO2 was determined by single-crystal X-ray diffraction. Crystal data: orthorhombic, space group Cmc2(1); a = 8.7001(2) A, b = 11.8497(3) A, and c = 11.7437(3) A; Z = 4; R1 = 0.0320 and wR2 = 0.1106. The structural, NMR, and vibrational spectroscopic properties of [Mn(CO)6]+ fit perfectly with those of the isoelectronic species [V(CO)6]-, Cr(CO)6, and [Fe(CO)6]2+.
ABSTRACT
The reaction of [Co(2)(CO)(8)] with (CF(3))(3)BCO in hexane leads to the Lewis acid-base adduct [Co(2)(CO)(7)CO--B(CF(3))(3)] in high yield. When the reaction is performed in anhydrous HF solution [Co(CO)(5)][(CF(3))(3)BF] is isolated. The product contains the first example of a homoleptic metal pentacarbonyl cation with 18 valence electrons and a trigonal-bipyramidal structure. Treatment of [Co(2)(CO)(8)] or [Co(CO)(3)NO] with NO(+) salts of weakly coordinating anions results in mixed crystals containing the [Co(CO)(5)](+)/[Co(CO)(2)(NO)(2)](+) ions or pure novel [Co(CO)(2)(NO)(2)](+) salts, respectively. This is a promising route to other new metal carbonyl nitrosyl cations or even homoleptic metal nitrosyl cations. All compounds were characterized by vibrational spectroscopy and by single-crystal X-ray diffraction.
ABSTRACT
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.
ABSTRACT
As the first examples of homoleptic, sigma-bonded superelectrophilic metal carbonyl cations with tetrafluoroborate [BF(4)](-) as the counter anions three thermally stable salts of the composition [M(CO)(6)][BF(4)](2) (M = Fe, Ru, Os) have been synthesized and extensively characterized by thermochemical, structural, and spectroscopic methods. A common synthetic route, the oxidative carbonylation of either Fe(CO)(5) (XeF(2) as the oxidizer) or M(3)(CO)(12) (M = Ru, Os) (F(2) as the oxidizer) in the conjugate Bronsted-Lewis superacid HF/BF(3), was employed. The thermal behavior of the three salts, studied by differential scanning calorimetry (DSC) and gas-phase IR spectroscopy of the decomposition products, has been compared to that of the corresponding [SbF(6)](-) salts. The molecular structures of [M(CO)(6)][BF(4)](2) (M = Fe, Os) were obtained by single-crystal X-ray diffraction at 100 K. X-ray powder diffraction data for [M(CO)(6)][BF(4)](2) (M = Ru, Os) were obtained between 100 and 300 K in intervals of 50 K. All three salts are isostructural and crystallized in the tetragonal space group I4/m (No. 87). As for the corresponding [M(CO)(6)][SbF(6)](2) salts (M = Fe, Ru, Os), similar unit cell parameters and vibrational fundamentals were also found for the three [BF(4)](-) compounds. For the structurally characterized salts [M(CO)(6)][BF(4)](2) (M = Fe, Os), very similar bond parameters for both cations and anions were found. Hence, the invariance of structural and spectroscopic properties of [M(CO)(6)](2+) cations (M = Fe, Ru, Os) extended from the fluoroantimonates [Sb(2)F(11)](-) and [SbF(6)](-) as counteranions also to [BF(4)](-).
ABSTRACT
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.
ABSTRACT
Predominantly sigma-bonded metal carbonyl cations (sigma-carbonyls) are conveniently generated in the Lewis superacid SbF(5) or the conjugate Brønsted-Lewis superacid HFbondSbF(5), primarily by solvolytic or reductive carbonylations. Thermally stable salts are formed with the fluoroantimonate(V) ions [SbF(6)](-) and [Sb(2)F(11)](-). The salts are characterised by analytical, structural, spectroscopic and computational methods. Most homoleptic carbonyl cations have very regular geometries, comensurate with their d-electron configurations: linear (d(10)), square planar (d(8)) or octahedral(d(6)). The cations with metals in oxidation states of +2 or +3 are termed "superelectrophilic". Extended molecular structures form by significant interionic C-F contacts with electrophilic carbon as acceptor. To account for all experimental observations, a conceptually simple synergetic bonding model is proposed. An outlook at anticipated future developments based on very recent results is provided.
ABSTRACT
Tris(trifluoromethyl)borane carbonyl, (CF(3))(3)BCO, is obtained in high yield by the solvolysis of K[B(CF(3))(4)] in concentrated sulfuric acid. The in situ hydrolysis of a single bonded CF(3) group is found to be a simple, unprecedented route to a new borane carbonyl. The related, thermally unstable borane carbonyl, (C(6)F(5))(3)BCO, is synthesized for comparison purposes by the isolation of (C(6)F(5))(3)B in a matrix of solid CO at 16 K and subsequent evaporation of excess CO at 40 K. The colorless liquid and vapor of (CF(3))(3)BCO decomposes slowly at room temperature. In the gas phase t(1/2) is found to be 45 min. In the presence of a large excess of (13)CO, the carbonyl substituent at boron undergoes exchange, which follows a first-order rate law. Its temperature dependence yields an activation energy (E(A)) of 112 kJ mol(-)(1). Low-pressure flash thermolysis of (CF(3))(3)BCO with subsequent isolation of the products in low-temperature matrixes, indicates a lower thermal stability of the (CF(3))(3)B fragment, than is found for (CF(3))(3)BCO. Toward nucleophiles (CF(3))(3)BCO reacts in two different ways: Depending on the nucleophilicity of the reagent and the stability of the adducts formed, nucleophilic substitution of CO or nucleophilic addition to the C atom of the carbonyl group are observed. A number of examples for both reaction types are presented in an overview. The molecular structure of (CF(3))(3)BCO in the gas phase is obtained by a combined microwave-electron diffraction analysis and in the solid state by single-crystal X-ray diffraction. The molecule possesses C(3) symmetry, since the three CF(3) groups are rotated off the two possible positions required for C(3)(v)() symmetry. All bond parameters, determined in the gas phase or in the solid state, are within their standard deviations in fair agreement, except for internuclear distances most noticeably the B-CO bond lengths, which is 1.69(2) A in the solid state and 1.617(12) A in the gas phase. A corresponding shift of nu(CO) from 2267 cm(-)(1) in the solid state to 2251 cm(-)(1) in the gas phase is noted in the vibrational spectra. The structural and vibrational study is supported by DFT calculations, which provide, in addition to the equilibrium structure, confirmation of experimental vibrational wavenumbers, IR-band intensities, atomic charge distribution, the dipole moment, the B-CO bond energy, and energies for the elimination of CF(2) from (CF(3))(x)()BF(3)(-)(x)(), x = 1-3. In the vibrational analysis 21 of the expected 26 fundamentals are observed experimentally. The (11)B-, (13)C-, and (19)F-NMR data, as well as the structural parameters of (CF(3))(3)BCO, are compared with those of related compounds.
ABSTRACT
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 Brønsted-Lewis superacid HF-SbF(5).
ABSTRACT
The oxidation of molybdenum hexacarbonyl, Mo(CO)(6), by antimony(V) fluoride, SbF(5), at 60 degrees C in an excess of liquid SbF(5), produces polymeric [{Mo(CO)(4)}(2)(cis-&mgr;-F(2)SbF(4))(3)](x)()[Sb(2)F(11)](x)() as the main product. Recrystallization from HF-SbF(5) produces orange prismatic crystals, suitable for a single-crystal X-ray diffraction study. Crystals of [{Mo(CO)(4)}(2)(cis-&mgr;-F(2)SbF(4))(3)](x)()[Sb(2)F(11)](x)() are monoclinic, space group P2(1)/c (No. 14), a = 9.234(4) Å, b = 13.858(3) Å, c = 25.790(3) Å, beta = 90.532(2) degrees, V = 3300.1(12) Å(3), and Z = 4. The structure was solved by the Patterson method and refined with anisotropic thermal parameters to R = 0.048 and R(w)() = 0.047 (on F, 472 variables, 5116 observations with I >/= 3sigma(I)). In the polymeric cation, two pyramidal Mo(CO)(4) groups are linked by bridging, iso-bidentate F(2)SbF(4) groups first into eight-membered rings, which are then further linked into polymeric chains. The bridging F(2)SbF(4) groups and the [Sb(2)F(11)](-) anion are involved in significant intermolecular and interionic F.C contacts to the C atoms of the Mo(CO)(4) groups.
ABSTRACT
The first carbonyl halogen cation in the condensed phase, the superelectrophilic [ClCO]+ ion, has been clearly and unambiguously established by its complete, fully assigned vibrational spectrum. The cation is obtained by the reaction of COCl2 with SbF5 at room temperature in the form of a suspension, in which it is stabilized by oligomeric fluoroantimonate ions.
ABSTRACT
Addition of carbon monoxide (0.5-2 atm) to iridium(III) fluorosulfate, Ir(SO(3)F)(3), dissolved in HSO(3)F over 4 days and at 60 degrees C, results in the quantitative formation of tris(carbonyl)iridium(III) fluorosulfate Ir(CO)(3)(SO(3)F)(3). Slow evaporation of the solvent produces single crystals of mer-Ir(CO)(3)(SO(3)F)(3). Crystal structure data for mer-Ir(CO)(3)(SO(3)F)(3): monoclinic, space group P2(1)/c, Z = 4, a = 8.476(1) Å, b = 12.868(2) Å, c = 12.588 (1) Å, beta = 108.24(1) degrees, V = 1304.0 Å(3), T = 200 K, R(F)() = 0.022 for 2090 data (I(o) >/= 2.5sigma(I(o))) and 200 variables. Vibrational spectra of the crystalline solid are consistent with a mer-isomer with CO stretching modes at 2249 (A(1)), 2208 (B(1)), and 2198 (A(1)) cm(-)(1) in the IR spectrum. In solution of HSO(3)F, additional CO stretching bands attributed to the fac-isomer are found in the FT-Raman and IR spectra at 2233 (A(1)) and 2157 cm(-)(1) (E). Additional evidence for a mixture of fac- and mer-isomers comes from (19)F NMR spectra. The vibrational spectra suggest strongly reduced iridium to CO pi-back-bonding. The crystal structure reveals significant intra- and intermolecular contacts between the electropositive C atom of the CO groups and O or F atoms of the fluorosulfate groups. Hence mer-tris(carbonyl)iridium(III) fluorosulfate becomes the first thermally stable, structurally characterized, and predominantly sigma-bonded carbonyl derivative of a metal in the +3 oxidation state.
