镧系金属一氢化物有效芯势研究

采用Cundari和Stevens等推导的有效芯势对镧系金属一氢化物进行了理论计算，以探讨镧系金属元素与氢的相互作用。结果表明所有镧系金属一氢化物基态时理论上是稳定的，最稳定的是SmH,最不稳定的是DyH;键长计算结果显示，基态时镧系金属一招兵买马花物有独立王国 收缩现象发生；红外振动频率理论计算值与实验结果一致；成键轨道中，金属原子轨道的贡献主要是s轨道和d轨道：从CeH至ErH(GdH)例外）随着外层电子的增加s轨道成分逐渐增大d轨道成分逐渐减小；从TmH和LuH（包括GdH)，成键轨道中金属原子轨道的贡献主要是d轨道，约为90％；约大多数镧系金属一氧化物的成键轨道中金属原子轨道f成分小于1％。     

Near infrared emission spectra of CoH and CoD

New high resolution emission spectra of CoH and CoD molecules have been recorded in the 640 nm to 3.5 μm region using a Fourier transform spectrometer. The bands were excited in a carbon tube furnace by the reaction of cobalt metal vapor and a mixture of H₂ or D₂ with He at a temperature of about 2600 °C. Eight bands were observed for the A′³Φ₄-X³Φ₄ electronic transition of CoD, and five bands for the corresponding transition of CoH. The (0, 0) bands of the A′³Φ₃-X³Φ₃ system were also recorded for both isotopologues, although one of the parity components in the X³Φ₃ sub-state of CoH was found to be perturbed. The A′³Φ₃-X³Φ₄ transition was also observed in our spectrum of CoH. In addition, a new [13.3]4 electronic state was found by observing [13.3]4-X³Φ₃ and [13.3]4-X³Φ₄ transitions in the spectrum of CoD. Analysis of the transitions with ΔΩ = 0, ± 1 provided more accurate values of spin-orbit splittings between Ω = 4 and Ω = 3 components. The ground-state data for both molecules were fitted both to band-constant and Dunham-expansion expressions, and a combined-isotopologue analysis of the X³Φ₄ spin component was carried out using the data for CoH and CoD. The upper states were represented by term values in these analyses because of perturbations, but estimated band constants for them were obtained in separate fits in which ground-state constants were held fixed.     

Theoretical investigation on the GaH molecule and its positive ion

The gallium monohydride (GaH) molecule and its positive ion were theoretically investigated by abinitio molecular orbital calculations with a flexible basis set including g-type functions on the Ga atom. Electron correlations among not only the valence electrons of Ga 4s4p and H 1s but also the semi-core electrons of Ga 3d were incorporated by a size-consistent scheme of the coupled pair approximation. The contribution of the 3d electron correlation was found to be considerable on spectroscopic constants of both GaH and GaH⁺, especially on the bond length. Received: 25 July 1997 / Accepted: 13 November 1997     

Monohydride-Dichloro Rhodium(III) Complexes with Chiral Diphosphine Ligands as Catalysts for Asymmetric Hydrogenation of Olefinic Substrates

We report full details of the synthesis and characterization of monohydride-dichloro rhodium(III) complexes bearing chiral diphosphine ligands, such as (S)-BINAP, (S)-DM-SEGPHOS, and (S)-DTBM-SEGPHOS, producing cationic triply chloride bridged dinuclear rhodium(III) complexes ( 1 a : (S)-BINAP; 1 b : (S)-DM-SEGPHOS) and a neutral mononuclear monohydride-dichloro rhodium(III) complex ( 1 c : (S)-DTBM-SEGPHOS) in high yield and high purity. Their solid state structure and solution behavior were determined by crystallographic studies as well as full spectral data, including DOSY NMR spectroscopy. Among these three complexes, 1 c has a rigid pocket surrounded by two chloride atoms bound to the rhodium atom together with one tBu group of (S)-DTBM-SEGPHOS for fitting to simple olefins without any coordinating functional groups. Complex 1 c exhibited superior catalytic activity and enantioselectivity for asymmetric hydrogenation of exo-olefins and olefinic substrates. The catalytic activity of 1 c was compared with that of well-demonstrated dihydride species derived in situ from rhodium(I) precursors such as [Rh(cod)Cl]₂ and [Rh(cod)₂]⁺[BF₄]⁻ upon mixing with (S)-DTBM-SEGPHOS under dihydrogen.     

Ab Initio Ground-State Potential Energy Function and Vibration-Rotation Energy Levels of Aluminum Monohydride

The accurate ground-state potential energy function of aluminum monohydride (AlH) has been determined from ab initio calculations using the multireference averaged coupled-pair functional (MR-ACPF) method in conjunction with the correlation-consistent core-valence basis sets up to septuple-zeta quality. The vibration-rotation energy levels of the two isotopologues, AlH and AlD, were predicted to near the “spectroscopic” accuracy. The importance of electron correlation beyond the MR-ACPF level of approximation, the scalar relativistic, spin-orbit, adiabatic, and nonadiabatic effects was discussed. © 2019 Wiley Periodicals, Inc.     

Interrupted thermal desorption of TiH2

Structural changes of commercial TiH₂ were studied using interrupted temperature desorption spectroscopy and X-ray diffraction techniques to understand the mechanism of its degradation under non-equilibrium conditions. Rapid cooling on different stages of temperature-programmed heating allowed to study the intermediate phase compositions that evolve upon cooling from the high-temperature phase βTi(H). The phase transformation sequence is described as a number of consecutive reactions corresponding to the observed desorption peaks. Phases δTiH_2−x, γTiH, and the solid solution αTi(H) were found to be intermediates in the TiH₂ → αTi transformation when the latter is interrupted. Additional evidence for the thermodynamic stability of γTiH is given.     

An analysis of the rotational, fine and hyperfine effects in the (0, 0) band of the AΠ-XΣ transition of manganese monohydride, MnH

High-resolution (±0.003 cm⁻¹), laser induced fluorescence (LIF) spectra of a supersonic molecular beam sample of manganese monohydride, MnH, have been recorded in the 17500-17800 cm⁻¹ region of the (0, 0) band of the A⁷Π-X⁷Σ ⁺ system. The low-N branch features were modeled successfully by inclusion of the magnetic hyperfine mixings of spin components within a given low-N rotational level using a traditional ‘effective’ Hamiltonian approach. An improved set of spectroscopic constants has been extracted and compared with those from previous analyses. The optimum optical features for future optical Stark and Zeeman measurements are identified.