Features of Protonation of the Simplest Weakly Basic Molecules,SO2, CO,N2O,CO2, and Others by Solid Carborane Superacids

An experimental study on protonation of simple weakly basic molecules (L) by the strongest solid superacid, H(CHB₁₁F₁₁), showed that basicity of SO₂ is high enough (during attachment to the acidic H atoms at partial pressure of 1 atm) to break the bridged H‐bonds of the polymeric acid and to form a mixture of solid mono‐ LH⁺⋅⋅⋅An⁻, and disolvates, L−H⁺−L. With a decrease in the basicity of L=CO (via C), N₂O, and CO (via O), only proton monosolvates are formed, which approach L−H⁺−An⁻ species with convergence of the strengths of bridged H‐bonds. The molecules with the weakest basicity, such as CO₂ and weaker, when attached to the proton, cannot break the bridged H‐bond of the polymeric superacid, and the interaction stops at stage of physical adsorption. It is shown here that under the conditions of acid monomerization, it is possible to protonate such weak bases as CO₂, N₂, and Xe.     

Comparison of electron impact and chemical ionization mass spectra of some arenetricarbonylchromium complexes

The mass spectrometric behavior of a) the tricarbonylchromium complexes of a series of aromatic hydrocarbons, b) the dimethyldiphenyl compounds of the Group IV elements (i.e., diphenylpropane, dimethyldiphenylsilane, etc.) and c) the mono- and bis-tricarbonylchromium complexes of these ligands under electron impact and chemical ionization conditions are reported. The MH⁺ ion is base peak for all of the simple arenetricarbonylchromium complexes using chemical ionization, whereas [M — 3 CO]⁺ or ⁵²Cr⁺ dominate the spectra with electron impact ionization. The chemical ionization spectra of the series of Group IV element ligands do not exhibit signals in the molecular ion region, the base peak being [M — Ph]⁺. [M — CH₃]⁺ is the electron impact base peak for each of the ligands except the lead-containing compound, for which the base peak is ²⁰⁸Pb⁺. The mono-tricarbonylchromium complexes yield chemical ionization molecular ion clusters, but their base peaks arise via fragmentation of the Group IV element—aromatic ring bonds. Electron impact ionization spectra of the mono complexes are characterized by losses of CO and the production of Cr⁺ ions, neither of which occurs with chemical ionization. For the series of bis-tricarbonylchromium complexes, an MH⁺ ion is prominent only in the chemical ionization spectrum of the diphenylpropane complex. The electron impact induced spectra of the bis-tricarbonylchromium complexes are similar to those of the mono-complexes in that loss of CO is a prominent feature.     

Comparative mass spectrometric investigation of transition metal polymethylcyclopentadienylcarbonyl complexes: II mass spectra of RnC5H5–nMN(CO)3 (R = CH3, n = 0–5; R = t-C(CH3)3, n = 1)

Investigation of π-(CH_3nC₅H_5–nMn(CO)₃ (Me_n-CpMnT) n = 0−5 and t-butyl CpMnT mass spectra showed that Me_nCpMnT molecular ion (M⁺) fragmentation occurs by a simpler scheme than that for Me_nCpReT M⁺ molecular ions. The reason is that MnCp and MnCO bonds are not as strong as the ReCp and ReCO bonds, and the relative “inertness” (compared to Re) of the Mn atom (ion), coordinated to the methylcyclopentadienyl ligand. Variations of M⁺ molecular ion intensity with different values of n are probably due to a complexity of electronic and spatial methyl-carbonyl group interactions in M⁺.     

Photoelectron Spectroscopy and Structures of X−⋅⋅⋅CH2O (X=F,Cl, Br,I) Complexes

A combined experimental and theoretical approach has been used to investigate X⁻⋅⋅⋅CH₂O (X=F, Cl, Br, I) complexes in the gas phase. Photoelectron spectroscopy, in tandem with time-of-flight mass spectrometry, has been used to determine electron binding energies for the Cl⁻⋅⋅⋅CH₂O, Br⁻⋅⋅⋅CH₂O, and I⁻⋅⋅⋅CH₂O species. Additionally, high-level CCSD(T) calculations found a C_2v minimum for these three anion complexes, with predicted electron detachment energies in excellent agreement with the experimental photoelectron spectra. F⁻⋅⋅⋅CH₂O was also studied theoretically, with a C_s hydrogen-bonded complex found to be the global minimum. Calculations extended to neutral X⋅⋅⋅CH₂O complexes, with the results of potential interest to atmospheric CH₂O chemistry.     

Field desorption mass spectra of [M(CO)3(η-arene)]X (MMn,Re; XBF4, PF6) salts

Field desorption mass spectra are reported for a range of [M(CO)₃(η-arene)]X (MMn or Re, XBF₄ or PF₆) salts. In most cases the spectra are simple, being dominated by molecular, [M]^+·, [M + 1]⁺, and [MCO]⁺ ions for the cationic part of their structure. However, with the π-chloroarene complexes [Mn(CO)₃(η-ClC₆H₅)]PF₆ and [Mn(CO)₃(η-1-Cl, 4-MeC₆H₄)]PF₆, facile loss of the chloro substituent and further fragmentation leads to unusually complex spectra, which include strong peaks arising from recombination of fragment species. Cluster ions are also noted in several cases, allowing identification of the anion.     

Potentiometric Investigation of the Weak Association of Sodium and Carbonate Ions at 25°C

The weak association between sodium and carbonate ions has been investigated at 25°C using high-precision sodium ion-selective electrode potentiometry in solutions of ionic strength ranging from 0.5 to 7.0 M in CsCl and in 1.0 M Me₄NCl media. The protonation constants of CO ₃ ^2- (aq) were also measured, using a H⁺-responsive glass electrode in 1.0 M Me₄NCl and NaCl. The value of the ion-pair association constant calculated from the difference in the protonation constants in these two media was in excellent agreement with that obtained from the Na⁺ISE measurements. Evidence is also presented for the formation of extremely weak ion pairs between Na⁺ and HCO ₃ ^- and between Cs⁺ and CO ₃ ^2- .     

[3+2] Cycloadditions of Metallo Nitrile Ylides and Metallo Nitrile Imines with Metal Carbonyl,Thiocarbonyl, and Isocyanide Complexes: Heterodimetallic Systems with Bridging Heterocycles [1]

The reactions of [Re(CO)₆]⁺, [FeCp(CO)₂CS]⁺ and [FeCp(CNPh)₃]⁺ with the metallo nitrile ylides [M^–{C⁺=N–C^–(H)CO₂Et}(CO)₅]^– (M = Cr, W) and the chromio nitrile imine [Cr^–{C⁺=N–N^–H}(CO)₅]^– (generated by mono‐α‐deprotonation of the parent isocyanide complexes) to give neutral 5‐metallated 1,3‐oxazolin‐ ( 1 ), 1,3‐thiazolin‐ ( 2 ), imidazolin‐ ( 3 , 4 ), 1,3,4‐oxdiazolin‐ ( 5 ), 1,3,4‐thiadiazolin‐ ( 6 ) and 1,3,4‐triazolin‐2‐ylidene ( 8 ) chromium and tungsten complexes represent the first all‐organometallic versions of Huisgen’s 1,3‐dipolar cycloadditions. The formation of 6 and 8 is accompanied by partial decomposition to (OC)₅Cr–C≡N–FeCpL₂ {L = CO ( 7 ), CNPh ( 9 )}. The structures of 4a and 5 have been characterized by X‐ray diffraction.     

Comparative mass spectrometric investigation of transition metal polymethylcyclopentadienylcarbonyl complexes: I. Mass spectra of RnC5H5−nRe(CO)3 (R = CH3, n = 0-5; R = t-C(CH3)3, n = 1)

Mass spectra of π-(CH₃)_nC₅H_5−nRe(CO)₃ Me_nCpReT) (n = 0–5) and t-BuCpReT were recorded, from which it was found that molecular ion (M⁺) fragmentation for Me_nCpReT (_n = 0, 1) differs from that for Me_nCpReT (_n = 2–5). The (M – 2CO)⁺ ions have maximum intensity in n = 0, 1 complexes, and the (M – 2CO – H₂)⁺ ions, in _n = 2–5 complexes. H₂ elimination from (M – 2CO)⁺ is typical of rhenium π-cyclopentadienyl complex fragmentation, where the number of methyl groups in the Cp ring is > 1, and seems to occur with participation of the Re atom.     

Towards clustered carbonyl cations [M3(CO)14]2+ (M = Ru,Os): the need for innocent deelectronation

To access the hitherto almost unknown class of clustered transition metal carbonyl cations, the trimetal dodecacarbonyls M₃(CO)₁₂ (M = Ru, Os) were reacted with the oxidant Ag⁺[WCA]⁻, but yielded the silver complexes [Ag{M₃(CO)₁₂}₂]⁺[WCA]⁻ (WCA = [Al(OR^F)₄]⁻, [F{Al(OR^F)₃}₂]⁻; R^F = –OC(CF₃)₃). Addition of further diiodine I₂ to increase the redox potential led for M = Ru non-specifically to divalent mixed iodo-Ru^II-carbonyl cations. With [NO]⁺, even the N–O bond was cleaved and led to the butterfly carbonyl complex cation [Ru₄N(CO)₁₃]⁺ in low yield. Obviously, ionization of M₃(CO)₁₂ with retention of its pseudo-binary composition including only M and CO is difficult and the inorganic reagents did react non-innocently. Yet, the radical cation of the commercially available perhalogenated anthracene derivative 9,10-dichlorooctafluoroanthracene (anthracene^Hal) is a straightforward accessible innocent deelectronator with a half-wave potential E_1/2 of 1.42 V vs. Fc^0/+. It deelectronates M₃(CO)₁₂ under a CO atmosphere and leads to the structurally characterized cluster salts [M₃(CO)₁₄]²⁺([WCA]⁻)₂ including a linear M₃ chain. The structural characterization as well as vibrational and NMR spectroscopies indicate the presence of three electronically independent sets of carbonyl ligands, which almost mimic M(CO)₅, free CO and even [M(CO)₆]²⁺ in one and the same cation.

Trimeric M₃(CO)₁₂ (M = Ru, Os) reacts with typical inorganic oxidants to unwanted side products. Yet, the 9,10-dichlorooctafluoroanthracene radical cation deelectronates these under CO pressure to give the first homotrimetallic [M₃(CO)₁₄]²⁺ salts.     

Dual Lewis Acid-Base Sites Regulate Silver-Copper Bimetallic Oxide Nanowires for Highly Selective Photoreduction of Carbon Dioxide to Methane

Highly selective photoreduction of CO₂ to valuable hydrocarbons is of great importance to achieving a carbon-neutral society. Precisely manipulating the formation of the Metal₁⋅⋅⋅C=O⋅⋅⋅Metal₂ (M₁⋅⋅⋅C=O⋅⋅⋅M₂) intermediate on the photocatalyst interface is the most critical step for regulating selectivity, while still a significant challenge. Herein, inspired by the polar electronic structure feature of CO₂ molecule, we propose a strategy whereby the Lewis acid-base dual sites confined in a bimetallic catalyst surface are conducive to forming a M₁⋅⋅⋅C=O⋅⋅⋅M₂ intermediate precisely, which can promote selectivity to hydrocarbon formation. Employing the Ag₂Cu₂O₃ nanowires with abundant Cu⋅⋅⋅Ag Lewis acid-base dual sites on the preferred exposed {110} surface as a model catalyst, 100 % selectivity toward photoreduction of CO₂ into CH₄ has been achieved. Subsequent surface-quenching experiments and density functional theory (DFT) calculations verify that the Cu⋅⋅⋅Ag Lewis acid-base dual sites do play a vital role in regulating the M₁⋅⋅⋅C=O⋅⋅⋅M₂ intermediate formation that is considered to be prone to convert CO₂ into hydrocarbons. This study reports a highly selective CO₂ photocatalyst, which was designed on the basis of a newly proposed theory for precise regulation of reaction intermediates. Our findings will stimulate further research on dual-site catalyst design for CO₂ reduction to hydrocarbons.     

Chemical Bonding in Homoleptic Carbonyl Cations [M{Fe(CO)5}2]+ (M=Cu,Ag, Au)

Syntheses of the copper and gold complexes [Cu{Fe(CO)₅}₂][SbF₆] and [Au{Fe(CO)₅}₂][HOB{3,5-(CF₃)₂C₆H₃}₃] containing the homoleptic carbonyl cations [M{Fe(CO)₅}₂]⁺ (M=Cu, Au) are reported. Structural data of the rare, trimetallic Cu₂Fe, Ag₂Fe and Au₂Fe complexes [Cu{Fe(CO)₅}₂][SbF₆], [Ag{Fe(CO)₅}₂][SbF₆] and [Au{Fe(CO)₅}₂][HOB{3,5-(CF₃)₂C₆H₃}₃] are also given. The silver and gold cations [M{Fe(CO)₅}₂]⁺ (M=Ag, Au) possess a nearly linear Fe-M-Fe’ moiety but the Fe-Cu-Fe’ in [Cu{Fe(CO)₅}₂][SbF₆] exhibits a significant bending angle of 147° due to the strong interaction with the [SbF₆]⁻ anion. The Fe(CO)₅ ligands adopt a distorted square-pyramidal geometry in the cations [M{Fe(CO)₅}₂]⁺, with the basal CO groups inclined towards M. The geometry optimization with DFT methods of the cations [M{Fe(CO)₅}₂]⁺ (M=Cu, Ag, Au) gives equilibrium structures with linear Fe-M-Fe’ fragments and D₂ symmetry for the copper and silver cations and D_4d symmetry for the gold cation. There is nearly free rotation of the Fe(CO)₅ ligands around the Fe-M-Fe’ axis. The calculated bond dissociation energies for the loss of both Fe(CO)₅ ligands from the cations [M{Fe(CO)₅}₂]⁺ show the order M=Au (D_e=137.2 kcal mol⁻¹)>Cu (D_e=109.0 kcal mol⁻¹)>Ag (D_e=92.4 kcal mol⁻¹). The QTAIM analysis shows bond paths and bond critical points for the M−Fe linkage but not between M and the CO ligands. The EDA-NOCV calculations suggest that the [Fe(CO)₅]→M⁺←[Fe(CO)₅] donation is significantly stronger than the [Fe(CO)₅]←M⁺→[Fe(CO)₅] backdonation. Inspection of the pairwise orbital interactions identifies four contributions for the charge donation of the Fe(CO)₅ ligands into the vacant (n)s and (n)p AOs of M⁺ and five components for the backdonation from the occupied (n-1)d AOs of M⁺ into vacant ligand orbitals.     

Halogenation behaviour of bidentate ligand-bridged derivatives of [Ru3(CO)12] and [Os3(CO)12]

Reaction of the ligand-bridged derivatives [M₃(CO)₁₀{μ-(RO)₂PN(Et)P(OR)₂}] and [M₃(CO)₈{μ-(RO)₂PN(Et)P(OR)₂}₂] (M = Ru or Os; R = Me or Prⁱ) with halogens leads to the formation of cationic products [M₃(μ-X)(CO)₁₀{μ- (RO)₂PN(Et)P(OR)₂}]⁺ and [M₃(μ-X)(CO)₈{μ-(RO)₂PN(Et)P(OR)₂}₂]⁺ (X = Cl, Br or I) in which the halogen bridges an opened edge of the metal atom framework; the crystal structure of [Ru₃(μ-I)(CO)₈{μ-(MeO)₂PN(Et)P(OMe)₂}₂]PF₆ is reported.     

Electron impact mass spectra of polycyclic aromatic compounds with several types of pyridino- and benzobenzanthrone skeletons

Electron impact mass spectra were measured for five isomers of pyridinobenzanthrones and three isomers of benzobenzanthrones. The fragmentation pattern and intensity of M²⁺, [M – H]⁺, [M – CO]ⁱ⁺, [M – CO – H(or 2H)]ⁱ⁺ and [M – CO – HCN]ⁱ⁺ (i = 1, 2) ions indicated remarkable differences and very interesting features according to the isomers with or without nitrogen and condensation positions of a pyridino or benzo ring to the benzanthrone skeleton. Further, the competition of decompositions through [M – H]⁺, [M – CO]^+˙ or [M – HCN]^+˙ ions was confirmed by the observation of metastable ions and the appearance energies of fragment ions. Interesting observations from these results were expulsion of an H atom in close proximity to the area around an O?C group, a weak bonding interaction between sp² C? H and an O?C group, inducing specific hydrogen rearrangement, and characteristic charge localization on heteroatoms.     

DFT Study of N_2O Activation with La~+, Hf~+, Ta~+ and W~+ in the Gas Phase

The spin‐forbidden reaction N₂O(X¹Δ)+M⁺→N₂ (X¹ Σ ⁺_g)+MO⁺(M⁺=La⁺, Hf⁺, Ta⁺, W⁺) was discussed using density functional theory. The reaction mechanism between M⁺ transition metal ions and N₂O is an insertion‐elimination one. All products are formed in exothermic processes. The potential energy curve crossings, which dramatically affect reaction mechanisms, were discussed in detail. In comparison with the previous work, an essential conclusion could be drawn that the reaction N₂O(X¹Δ)+CO(¹Δ⁺)→N₂(X¹ Σ ⁺_g)+CO₂(¹ Σ ⁺_g) catalyzed by M⁺ was endothermic by 358.89 kJ·mol^?1 which is in accord with the experiment finding.     

Reaction Behavior of Decacarbonyldimetalates(2‐) (M = Cr and Mo) towards the Nitrosyl Carbonyls of Iron and Cobalt

The reaction of the nitrosyl carbonyl complexes [Fe(NO)₂(CO)₂] and [Co(NO)(CO)₃] with the decacarbonyldimetalates [M₂(CO)₁₀]^2– (M = Cr and Mo) in THF as the solvent at room temperature was investigated. Thereby a substitution of one nitrosyl ligand towards carbon monoxide was observed in each case. Both reactions afforded the known metalate complexes [Fe(NO)(CO)₃]^– and [Co(CO)₄]^–, respectively. These species were isolated as their corresponding PPN salts [PPN⁺ = bis(triphenylphosphane)iminium cation] in nearly quantitative yields. The products were unambiguously identified by their IR spectroscopic and elemental analytic data as well as by their characteristic colors and melting points.     

Positive/negative liquid secondary ion mass spectrometry ofLn-EDTA (1:1) complexes. Formation of molecular ion adducts with neutral species of the matrix orLn-EDTA

Summary The mass spectra of 1:1 complexes ofEDTA with lanthanide cations (Ln=Sm, Eu, Gd, Tb or Dy) upon positive/negative LSIMS are presented. In glycerol used as a matrix, adduct-ions such as [M+H]⁺, [M+H+nGly]⁺, [2M+H]⁺, [2M+H+Gly]⁺ (positive LSIMS) or [M-H]^–, [M-H+nGly]^–, [2M-H]^–, [2M-H+Gly]^– (negative LSIMS), wheren=1–3, are formed. Reactions leading to the formation of adduct-ions are suggested.

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Positive/negative Liquid-Sekundärionen-Massenspektrometrie vonLn-EDTA-(1:1)-Komplexen. Bildung von molekularen Ionenaddukten mit neutralen Spezies aus der Matrix oderLn-EDTA

Zusammenfassung Die Massenspektren von 1:1-Komplexen vonEDTA mit Lanthanidenkationen (Ln=Sm, Eu, Gd, Tb oder Dy) mittels positiver/negativer LSIMS werden präsentiert. In Glycerin als Matrix bilden sich Adduktionen wie [M+H]⁺, [M+H+nGly]⁺, [2M+H]⁺, [2M+H+Gly]⁺ (positive LSIMS) oder [M-H]^–, [M-H+nGly]^–, [2M-H]^–, [2M-H+Gly]^– (negative LSIMS), wobein=1–3. Es werden Reaktionen vorgeschlagen, die zur Bildung von Adduktionen führen.

     

Study of the intensity of M+, M2+ and MO+ signals in ICP-MS as a function of instrumental parameters

In addition to peaks from singly charged ions (M⁺), signals from oxide (MO⁺), hydroxide (MOH⁺) and doubly charged (M²⁺) ions, which may lead to spectral overlap interferences, are observed in ICP-MS spectra. Using a VG PlasmaQuad ratios of MO⁺/M⁺, MOH⁺/M⁺ and M²⁺/M⁺ were determined for a number of elements, covering a wide range of atomic masses, first and second ionisation energies and chemical properties. The temporal stability of the MO⁺/M⁺ and M²⁺/M⁺ ratios was investigated. The correlation between the ratios of MO⁺/M⁺ and M²⁺/M⁺ with the M-O bond strength and the difference between the second and the first ionisation energy respectively is discussed. The influence of several instrumental parameters, associated with sample introduction and plasma operation, on the M⁺, M²⁺ and MO⁺ signals and on the MO⁺/M⁺ and M²⁺/M⁺ ratios is studied. Simple qualitative explanations are given in order to explain some of the observed results. No quantitative results are given for the MO⁺/M⁺ and M²⁺/M⁺ ratios as the experiments pointed out that they are influenced to a large extent by several instrumental parameters.     

Cluster Chemistry: XXVIII. Utility of fast atom bombardment mass spectrometry for the characterisation of high molecular weight complexes containing metal clusters

Fast atom bombardment (FAB) mass spectrometry has been used to obtain spectra of HRu₃Au(μ₃-S)(CO)₉(PPh₃), Ru₃Au₂(μ₃-S)(CO)₉(PPh₃)₂ and Ru₃Au₃(μ₃-C₁₂H₁₅)(CO)₈(PPh₃)₃, none of which give metal-containing ions in conventional EI mass spectrometry. All the compounds give molecular (M⁺) or quasimolecular ([M + 2H]⁺) ions which fragment by conventional routes.     

Übergangsmetall-Fulven-Komplexe: XXXII. Heteronukleare Zweikernkomplexe des Azulens

The molecular structure of the dinuclear complex [(η⁶-benzene)M$\text{o(μ-η}{}^6\text{: η}{}^4\text{-azulene)C}$r(CO)₃ was determined by an X-ray diffraction study. The reaction of [(η⁶-azulene)(η⁶-benzene)Mo] with [RhCI(CO)₂]₂ gives the salt [η⁶-benzene)M$\text{o(μ-η}{}^6\text{: η}{}^4\text{-azulene)R}$h(CO)₂]₊[RhCl₂(CO)₂]^?, the structure of which was also characterized by X-ray crystallography. The cation of this salt can also be synthesized from [(η⁶-azulene)(η⁶-benzene)Mo] and [Rh(CO)₂]⁺. The fluxionality of the cation was studied by temperature-dependent ¹H-NMR measurements. The complex [(η⁶-azulene)(η⁶-benzene)Mo] reacts with Fe₂(CO)₉ to give the dinuclear complex [(η⁶-benzene)M$\text{o(μ-η}{}^5\text{:}{}_3\text{-azulene)F}$e(CO)₃], as confirmed by X-ray diffraction.     

Organometallic Lewis Acids,Part LXII. Chiral Carbonyl‐Cyclopentadienyl‐Triphenylphosphine‐Iron and ‐Ruthenium Complexes with Tertiary Nitriles [CpM(CO)(PPh3)(N≡C–CR1R2R3)]+ BF4– (M = Fe,Ru)

A series of tertiary nitriles was synthesized by alkylation of acetonitrile, primary and secondary nitriles, using alkylbromides and sodium amide in liquid ammonia. By reaction of the in situ formed organometallic Lewis acids [CpM(CO)(PPh₃)]⁺ (M = Fe, Ru) with the novel tertiary nitriles, the complexes [CpM(CO)(PPh₃)(N≡C–CR¹R²R³]BF₄ were obtained. A di‐iron complex was formed with 1,6‐dicyanohexane.