Guided Ion Beam and Theoretical Studies of the Reactions of Pd+ with CS2: Thermochemistry of PdS+ and PdCS+

Thermochemistry and mechanisms of the Pt+ + SO2 reaction from guided ion beam tandem mass spectrometry and theory

The kinetic energy dependences of the reactions of Pt⁺ (²D_5/2) with SO₂ were studied using a guided ion beam tandem mass spectrometer and theory. The observed cationic products are PtO⁺ and PtSO⁺, with small amounts of PtS⁺, all formed in endothermic reactions. Modeling the kinetic energy dependent product cross sections allows determination of the product bond dissociation energies (BDEs): D₀(Pt⁺-O) = 3.14 ± 0.11 eV, D₀(Pt⁺-S) = 3.68 ± 0.31 eV, and D₀(Pt⁺-SO) = 3.03 ± 0.12 eV. The oxide BDE agrees well with more precise literature values, whereas the latter two results are the first such measurements. Quantum mechanical calculations were performed for PtO⁺, PtS⁺, PtO₂ ⁺, and PtSO⁺ at the B3LYP and coupled-cluster with single, double, and perturbative triple [CCSD(T)] levels of theory using the def2-XZVPPD (X = T, Q) and aug-cc-pVXZ (X = T, Q, 5) basis sets and complete basis set extrapolations. These theoretical BDEs agree well with the experimental values. After including empirical spin-orbit corrections, the product ground states are determined as PtO⁺ (⁴Σ_3/2), PtS⁺ (⁴Σ_3/2), PtO₂ ⁺ (²Σ_g ⁺), and PtSO⁺ (²A'). Potential energy profiles including intermediates and transition states for each reaction were also calculated at the B3LYP/def2-TZVPPD level. Periodic trends in the thermochemistry of the group 9 metal chalcogenide cations are compared, and the formation of PtO⁺ from the Pt⁺ + SO₂ reaction is compared with those from the Pt⁺ + O₂, CO₂, CO, and NO reactions.

Gold with +4 oxidation state compounds: mass spectrometric and theoretical characterization of AuO2+

Using an ab initio methodology and mass spectrometric study we identify AuO²⁺ as a metastable species in the gas phase.

Submerged Barriers in the Ni(+) Assisted Decomposition of Propionaldehyde

The reaction dynamics of the Ni(+) mediated decarbonylation of propionaldehyde was assessed using the single photon initiated decomposition rearrangement reaction (SPIDRR) technique. The exothermic production of Ni(+)CO was temporally monitored and the associated rate constants, k(E), were extracted as a function of activating photon energy. In addition, the reaction potential energy surface was calculated at the UCCSD(T)/def2-TZVP//PBEPBE/cc-pVDZ level of theory to provide an atomistic description of the reaction profile. The decarbonylation of propionaldehyde can be understood as proceeding through parallel competitive reaction pathways that are initiated by Ni(+) insertion into either the C-C or C-H bond of the propionaldehyde carbonyl carbon. Both paths lead to the elimination of neutral ethane and are governed by submerged barriers. The lower energy sequence is a consecutive C-C/C-H addition process with a submerged barrier of 14 350 ± 600 cm(-1). The higher energy sequence is a consecutive C-H/C-C addition process with a submerged barrier of 15 400 ± 600 cm(-1). Both barriers were determined using RRKM calculations fit to the experimentally determined k(E) values. The measured energy difference between the two barriers agrees with the DFT computed difference in rate limiting transition-state energies, 18 413 and 19 495 cm(-1).

Cationic Noncovalent Interactions: Energetics and Periodic Trends

In this review, noncovalent interactions of ions with neutral molecules are discussed. After defining the scope of the article, which excludes anionic and most protonated systems, methods associated with measuring thermodynamic information for such systems are briefly recounted. An extensive set of tables detailing available thermodynamic information for the noncovalent interactions of metal cations with a host of ligands is provided. Ligands include small molecules (H2, NH3, CO, CS, H2O, CH3CN, and others), organic ligands (O- and N-donors, crown ethers and related molecules, MALDI matrix molecules), π-ligands (alkenes, alkynes, benzene, and substituted benzenes), miscellaneous inorganic ligands, and biological systems (amino acids, peptides, sugars, nucleobases, nucleosides, and nucleotides). Hydration of metalated biological systems is also included along with selected proton-based systems: 18-crown-6 polyether with protonated peptides and base-pairing energies of nucleobases. In all cases, the literature thermochemistry is evaluated and, in many cases, reanchored or adjusted to 0 K bond dissociation energies. Trends in these values are discussed and related to a variety of simple molecular concepts.

The dehydrogenation of alcohols and hydrocarbons by atomic metal anions

The reactivity of anionic metal-carbonyl systems toward hydrocarbons, alcohols and a variety of other classes of molecules is well established in the literature. In this study we explored the reactions of atomic metal anions M(-), notably K(-), Cs(-), Co(-), Fe(-), Cu(-) and Ag(-), with alcohols, alkanes, alkenes and alkynes. All of the metal anions deprotonated the alcohols and alkynes. Also observed were the subsequent reactions of the resulting organic anions. Fe(-) and Cu(-) consistently displayed mono- and bis-dehydrogenation of primary and secondary alcohols, and alkanes, alkenes and alkynes to form MH(-) and MH(2)(-). Mechanisms for the dehydrogenation reactions are proposed and substantiated with isotopically-labelled reagents and thermochemical arguments.