Heavy hydrides: H2Te ultraviolet photochemistry

The highly exothermic hydrogen abstraction reaction H2Te + OH → H2O + TeH: comparison with analogous reactions for H2Se and H2S

The "gold standard" CCSD(T) method is adopted along with the correlation consistent basis sets up to aug-cc-pV5Z-PP to study the mechanism of the hydrogen abstraction reaction H₂Te + OH. The predicted geometries and vibrational frequencies for reactants and products are in good agreement with the available experimental results. With the ZPVE corrections, the transition state in the favorable pathway of this reaction energetically lies 1.2 kcal mol^-1 below the reactants, which is lower than the analogous relative energies for the H₂Se + OH reaction (-0.7 kcal mol^-1), the H₂S + OH reaction (+0.8 kcal mol^-1) and the H₂O + OH reaction (+9.0 kcal mol^-1). Accordingly, the exothermic reaction energies for these related reactions are predicted to be 47.8 (H₂Te), 37.7 (H₂Se), 27.1 (H₂S), and 0.0 (H₂O) kcal mol^-1, respectively. Geometrically, the low-lying reactant complexes for H₂Te + OH and H₂Se + OH are two-center three-electron hemibonded structures, whereas those for H₂S + OH and H₂O + OH are hydrogen-bonded. With ZPVE and spin-orbit coupling corrections, the relative energies for the reactant complex, transition state, product complex, and the products for the H₂Te + OH reaction are estimated to be -13.1, -1.0, -52.0, and -52.6 kcal mol^-1, respectively. Finally, twenty-eight DFT functionals have been tested systematically to assess their ability in describing the potential energy surface of the H₂Te + OH reaction. The best of these functionals for the corresponding energtics are -9.9, -1.4, -46.4, and -45.4 kcal mol^-1 (MPWB1K), or -13.1, -2.4, -57.1, and -54.6 kcal mol^-1 (M06-2X), respectively.

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Reagents that Contain Se-H or Te-H Bonds

Species that contain bonds between hydrogen and selenium or tellurium have a characteristic high reactivity, which can be harnessed in the synthesis of valuable organic compounds. This overview includes the synthesis of dihydrides, alkali metal hydrochalcogenides, chalcogenols, chalcogenocarboxylic and chalcogenocarbamic acids, and their application in reactions of reduction, addition to unsaturated compounds, and nucleophilic substitution.

Using anisotropy measurements from A-band photodissociation to interrogate the excited states of H2Se

The A-band photodissociation of H2Se has been studied by measuring H-atom velocity-aligned Doppler spectroscopy (VADS) spectra at five wavelengths from 210 to 266 nm. These spectra have been subsequently simulated by assigning cross-sections and anisotropy β values to the two SeH spin-orbit exit channels. While the SeH((2)Π3/2) exit channel has a β value close to -1 throughout the studied wavelength range, the spin-orbit excited SeH((2)Π1/2) exit channel's β value switches from near -1 to near +0.5 when the photolysis wavelength increases from 210 to 266 nm. These results have been examined in the light of available ab initio calculations. Throughout the studied wavelengths, the contribution from excitation to the 1(1)B1 state predominates and provides the source of the -1 β value. In order to account for the +0.5 β value, it is necessary to assume that the 2(1)A1 state as well as the 4A' and 5A' states (both originating from a (3)B1 state) also contribute at short wavelengths. More interestingly, at the longer wavelength end (266 nm), contribution of a +0.5 β value from the 3A' state (originating from a (3)A2 state) exceeds the contribution of the -1 β value for the SeH((2)Π1/2) channel.

Nonadiabatic photodissociation dynamics in (HI)2 induced by intracluster collisions

The sequential photodissociation dynamics of (HI)2 is studied by means of a nonadiabatic wave packet treatment starting from the I*-HI complex. The model reproduces the main experimental findings for photolysis with 266 nm radiation. The results confirm that some of the H atoms dissociated from the I*-HI complex deactivate the I* atom through a HI* intracluster collision which induces an I*-->I electronically nonadiabatic transition. As a consequence, these H fragments become very fast by acquiring nearly all the I* excitation energy, equivalent to the I*I spin-orbit splitting. A most interesting result is the high production of bound I2 fragments in highly excited rovibrational states in the photolysis, indicating that the H dissociation is mainly direct.

State-to-state reaction dynamics: A selective review

A selective review of state-to-state reaction dynamics experiments is presented. The review focuses on three classes of reactions that exemplify the rich history and illustrate the current state of the art in such work. These three reactions are (1) the hydrogen exchange reaction, H+H2-->H2+H and its isotopomers; (2) the H+RH-->H2+R reactions, where RH is an alkane, beginning with H+CH4-->H2+CH3 and extending to much larger alkanes; and (3) the Cl+RH-->HCl+R reactions, principally Cl+CH4-->HCl+CH3. We describe the experiments, discuss their results, present comparisons with theory, and introduce heuristic models.