Theoretical study in [C2H4–Tl]+ and [C2H2–Tl]+ complexes

We studied the attraction between [C₂H_n] and Tl(I) in the hypothetical [C₂H_n–Tl]⁺ complexes (n = 2,4) using ab initio methodology. We found that the changes around the equilibrium distance C–Tl and in the interaction energies are sensitive to the electron correlation potential. We evaluated these effects using several levels of theory, including Hartree–Fock (HF), second‐order Møller–Plesset (MP2), MP4, coupled cluster singles and doubles CCSD(T), and local density approximation augmented by nonlocal corrections for exchange and correlation due to Becke and Perdew (LDA/BP). The obtained interaction energies differences at the equilibrium distance R_e (C–Tl) range from 33 and 46 kJ/mol at the different levels used. These results indicate that the interaction between olefinic systems and Tl(I) are a real minimum on the potential energy surfaces (PES). We can predict that these new complexes are viable for synthesizing. At long distances, the behavior of the [C₂H_n]–Tl⁺ interaction may be related mainly to charge‐induced dipole and dispersion terms, both involving the individual properties of the olefinic π‐system and thallium ion. However, the charge‐induced dipole term (R^?4) is found as the principal contribution in the stability at long and short distances. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Co‐Adsorption of O2 and CO on Au2−: Infrared Photodissociation Spectroscopy and Theoretical Study of [Au2O2(CO)n]− (n=2–6)

The co‐adsorption of O₂ and CO on anionic sites of gold species is considered as a crucial step in the catalytic CO oxidation on gold catalysts. In this regard, the [Au₂O₂(CO)_n]^? (n=2–6) complexes were prepared by using a laser vaporization supersonic ion source and were studied by using infrared photodissociation spectroscopy in the gas phase. All the [Au₂O₂(CO)_n]^? (n=2–6) complexes were characterized to have a core structure involving one CO and one O₂ molecule co‐adsorbed on Au₂^? with the other CO molecules physically tagged around. The CO stretching frequency of the [Au₂O₂(CO)]^? core ion is observed around =2032–2042 cm^?1, which is about 200 cm^?1 higher than that in [Au₂(CO)₂]^?. This frequency difference and the analyses based on density functional calculations provide direct evidence for the synergy effect of the chemically adsorbed O₂ and CO. The low lying structures with carbonate group were not observed experimentally because of high formation barriers. The structures and the stability (i.e., the inertness in a sense) of the co‐adsorbed O₂ and CO on Au₂^? may have relevance to the elementary reaction steps on real gold catalysts.     

The Protonation of Acetamide and Thioacetamide in Super­acidic Solutions: Crystal Structures of [H3CC(OH)NH2]+AsF6– and [H3CC(SH)NH2]+AsF6–

Acetamide and thioacetamide react with the superacid solutions HF/MF₅ (M = As, Sb) under formation of the corresponding salts [H₃CC(OH)NH₂]⁺MF₆^– and [H₃CC(SH)NH₂]⁺MF₆^– (M = As, Sb), respectively. The reaction of DF/AsF₅ with acetamide and thioacetamide lead to the corresponding deuterated salts [H₃CC(OD)ND₂]⁺AsF₆^– and [H₃CC(SD)ND₂]⁺AsF₆^–, respectively_. The salts are characterized by vibrational and NMR spectroscopy, and in the case of [H₃CC(OH)NH₂]⁺AsF₆^– and [H₃CC(SH)NH₂]⁺AsF₆^– also by single‐crystal X‐ray analyses. The [H₃CC(OH)NH₂]⁺AsF₆^– ( 1 ) salt crystallizes in the triclinic space group P$\bar{1}$ with two formula units per unit cell, and the [H₃CC(SH)NH₂]⁺AsF₆^– ( 2 ) salt crystallizes in the monoclinic space group P2₁/c with four formula units per unit cell. In both crystal structures three‐dimensional networks are observed which are formed by intra‐ and intermolecular N–H ··· F and O–H ··· F or S–H ··· F hydrogen bonds, respectively. For the vibrational analyses, quantum chemically calculated spectra of the cations [H₃CC(OH)NH₂ · 3HF]⁺ and [H₃CC(SH)NH₂ · 2HF]⁺ are considered.