Infrared Spectroscopy of [M(CO₂)_<i>n</i>]⁺ (M = Ca, Sr, and Ba; <i>n</i> = 1–4) in the Gas Phase: Solvation-Induced Electron Transfer and Activation of CO₂

Cationic complexes of heavy alkaline earth metal and carbon dioxide [M(CO2)n]+ (M = Ca, Sr, and Ba) are produced by a laser vaporization-supersonic expansion ion source in the gas phase and are studied by infrared photodissociation spectroscopy in conjunction with quantum chemistry calculations. For the n = 1 complexes, the metal–ligand binding arises primarily from the electrostatic interaction with the CO2 ligand bound to the metal (+I) center in an end-on η1-O fashion. The more highly coordinated complexes [M(CO2)n]+ with n ≥ 2 are characterized to involve a [M2+(CO2–)] core ion with the CO2– ligand bound to the metal (+II) center in a bidentate η2-O, O manner. The activation of CO2 in forming a bent CO2– moiety occurs via solvation-induced metal cation-ligand electron transfer reactions. Bonding analyses reveal that the attractive forces between M2+ and CO2– in the core cation come mainly from electrostatic attraction, but the contribution of covalent orbital interactions should not be underestimated. The atomic orbitals of metal dications that are engaged in the orbital interactions are ns and (n – 1)d orbitals

Reactions of Vanadium Dioxide Molecules with Acetylene: Infrared Spectra of VO₂(η²‑C₂H₂)_<i>x</i> (<i>x</i> = 1, 2) and OV(OH)CCH in Solid Neon

Reactions of vanadium dioxide molecules with acetylene have been studied by matrix isolation infrared spectroscopy. Reaction intermediates and products are identified on the basis of isotopic substitutions as well as density functional frequency calculations. Ground state vanadium dioxide molecule reacts with acetylene in forming the side-on-bonded VO₂(η²-C₂H₂) and VO₂(η²-C₂H₂)₂ complexes spontaneously on annealing in solid neon. The VO₂(η²-C₂H₂) complex is characterized to have a ²B₂ ground state with <i>C</i>_2<i>v</i> symmetry, whereas the VO₂(η²-C₂H₂)₂ complex has a ²A ground state with <i>C</i>₂ symmetry. The VO₂(η²-C₂H₂) and VO₂(η²-C₂H₂)₂ complexes are photosensitive. The VO₂(η²-C₂H₂) complex rearranges to the OV­(OH)­CCH molecule upon UV–vis light excitation

Infrared Photodissociation Spectroscopy and Density Functional Theory Study of Carbon Suboxide Complexes [M(CO)₄(C₃O₂)]⁺ (M = Fe, Co, Ni)

Infrared photodissociation spectra are measured for mass-selected cation complexes with a chemical formula [MC₇O₆]⁺ (M = Fe, Co, Ni) formed via pulsed laser evaporation of metal target in expansions of helium gas seeded by CO. The geometries of the complexes are determined by comparison of the experimental spectra with the simulated spectra from density functional calculations. All of these complexes are identified to have [M­(CO)₄(C₃O₂)]⁺ structures involving a carbon suboxide ligand, which binds the metal center in an η¹ fashion. The antisymmetric CO stretching vibration of C₃O₂ is slightly red-shifted upon coordination. The donor–acceptor bonding interactions between C₃O₂ and the metal centers are analyzed using the EDA-NOCV method. The results show that M ← C₃O₂ σ donation is stronger than the M → C₃O₂ π back-donation in these cation complexes

Infrared Spectra and Structures of the Neutral and Charged CrCO₂ and Cr(CO₂)₂ Isomers in Solid Neon

The reactions from codeposition of laser-ablated chromium atoms with carbon dioxide in excess neon are studied by infrared absorption spectroscopy. The species formed are identified by the effects of isotopic substitution on their infrared spectra. Density functional calculations are performed to support the spectral assignments and to interpret the geometric and electronic structures of the experimentally observed species. Besides the previously reported insertion products OCrCO and O₂Cr­(CO)₂, the one-to-one Cr­(CO₂) complex and the one-to-two Cr­(CO₂)₂ complex as well as the CrOCrCO and OCCrCO₃ complexes are also formed. The Cr­(CO₂) complex is characterized to be side-on η²-C,O-coordinated. The Cr­(CO₂)₂ complex is identified to involve a side-on η²-C,O-coordinated CO₂ and an end-on η¹-O-coordinated CO₂. OCCrCO₃ is a carbonate carbonyl complex predicted to have a planar structure with a η²-O,O-coordinated carbonate ligand. The CrOCrCO complex is predicted to be linear with a high-spin ground state. Besides the neutral molecules, charged species are also produced. The Cr­(CO₂)⁺ and Cr­(CO₂)₂⁺ cation complexes are characterized to have linear end-on η¹-O-coordinated structures with blue-shifted antisymmetric CO₂ stretching vibrational frequencies. The OCrCO^– anion is bent with the Cr–O and CO stretching frequencies red-shifted from those of OCrCO neutral molecule

W. Lester S. Andrews Preface

W. Lester S. Andrews Prefac

Infrared Photodissociation Spectroscopic and Theoretical Study of Heteronuclear Transition Metal Carbonyl Cluster Cations in the Gas Phase

Heteronuclear transition metal carbonyl cluster cations FeM­(CO)₈⁺ (M = Co, Ni and Cu) and MCu­(CO)₇⁺ (M = Co and Ni) are produced via a laser vaporization supersonic cluster ion source in the gas phase, which are each mass-selected and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are established by comparison of the experimental spectra with those derived from density functional theoretical calculations. The FeM­(CO)₈⁺ (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)₅Fe–M­(CO)₃⁺ structures, and the MCu­(CO)₇⁺ (M = Co, Ni) ions are characterized to have staggered (CO)₄M–Cu­(CO)₃⁺ structures. Natural bonding orbital analysis indicates that the positive charge is mainly distributed on the M­(CO)₃ fragment. The metal–metal interaction involves an σ-type (OC)_4,5M→M­(CO)₃⁺ dative bonding

Isocyanate Formation from Reactions of Early Lanthanide Metal Atoms with NO and CO in Solid Argon

The reactions of early lanthanide metal atoms (Ce, Pr, and Nd) with carbon monoxide and nitric oxide mixtures are studied by infrared absorption spectroscopy in solid argon. The reaction intermediates and products are identified via isotopic substitution as well as theoretical frequency calculations. The results show that the reactions proceed with the initial formation of inserted NLnO molecules, which subsequently react with CO to form the NLnO­(CO) complexes on annealing. The NLnO­(CO) complexes further isomerize to the more stable isocyanate OLnNCO species under UV light excitation

Coordination and Solvation of the Au⁺ Cation: Infrared Photodissociation Spectroscopy of Mass-Selected Au(H₂O)_<i>n</i>⁺ (<i>n</i> = 1–8) Complexes

Gold cation–water complexes with attached argon atoms are produced via a laser vaporization supersonic cluster source. The [Au­(H₂O)_<i>n</i>Ar_<i>x</i>]⁺ (<i>n</i> = 1–8; <i>x</i> = 1 or 2) complexes are each mass selected and studied by infrared photodissociation spectroscopy in the OH stretching frequency region to explore the coordination and solvation structures of the Au⁺ cation. Density functional calculations have been performed, and the calculated vibrational spectra are compared to the experimental spectra to identify the gas-phase structures of the Au­(H₂O)_<i>n</i>⁺ complexes. Confirming previous theoretical predications, the first coordination shell of the Au⁺ cation contains two water molecules forming a linear O–Au⁺–O arrangement; subsequent water molecules bind to the two H₂O ligands of the Au­(H₂O)₂⁺ core ion via hydrogen bond forming of the second hydration shell, which is complete at <i>n</i> = 6. For the complexes with <i>n</i> ≤ 7, the experimental spectrum can in general be assigned to the predicted global minimum structure. However, the spectrum suggests that two or more conformers coexist for the <i>n</i> = 8 complex, indicating that the identification of a single global minimum becomes less important upon increasing the number of solvating water molecules

Infrared Photodissociation Spectroscopy of Heterodinuclear Iron–Zinc and Cobalt–Zinc Carbonyl Cation Complexes

Fe–Zn and Co–Zn heteronuclear carbonyl cation complexes are produced via a laser vaporization supersonic cluster source in the gas phase. The dinuclear FeZn­(CO)₅⁺ and CoZn­(CO)₇⁺ cation complexes are observed to be the most intense heterodinuclear carbonyl cation species in the mass spectra. The infrared spectra are obtained via mass selection and infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are assigned with the support of density functional calculations. The FeZn­(CO)₅⁺ complex is determined to have a (OC)₅Fe–Zn structure with a Fe–Zn half bond. The CoZn­(CO)₇⁺ ion is established to have a staggered (OC)₄Co–Zn­(CO)₃ structure involving a Co–Zn σ single bond

Carbon Dioxide Activation by Scandium Atoms and Scandium Monoxide Molecules: Formation and Spectroscopic Characterization of ScCO₃ and OCScCO₃ in Solid Neon

The reactions of carbon dioxide with scandium monoxide molecules and scandium atoms are investigated using matrix isolation infrared spectroscopy in solid neon. The species formed are identified by the effects of isotopic substitution on their infrared spectra as well as density functional calculations. The results show that the ground state ScO molecule reacts with carbon dioxide to form the carbonate complex ScCO₃ spontaneously on annealing. The ground state Sc atom reacts with two carbon dioxide molecules to give the carbonate carbonyl complex OCScCO₃ via the previously reported OScCO insertion intermediate on annealing. The observation of these spontaneous reactions is consistent with theoretical predictions that both the Sc + 2CO₂ → OCScCO₃ and ScO + CO₂ → ScCO₃ reactions are thermodynamically exothermic and are kinetically facile, requiring little or no activation energy