Study of Dehydrocoupling Reactions of Diorganotin Dihydrides R^1R^2SnH2 with Biuret

The reaction of unsymmetrical phenylmethyltin dihydride （PhMeSnH2）, phenylethyltin dihydride （PhEtSnH2）, phenylbutyltin dihydride （PhBuSnH2） and butylmethyltin dihydride （BuMeSnH2） with biuret （HAL） proceeds via SnH/NH dehydrocoupling to afford the corresponding tetra-coordinate cyclic products. The reactions in the molar ratios of 1 ： 1, 2 ： 1 and 1 ： 2 have been studied. The yellow derivatives so isolated were soluble in polar solvents and insoluble in nonpolar solvents. It was found that 1 ： 1 reaction went to completion while 2 ： 1 and 1 ： 2 did not go to completion. The derivatives had been characterized by elemental analysis and spectroscopic techniques viz. IR, ^1H NMR, ^13C NMR, ^119Sn NMR. DSC and TGA of the reaction products have also been studied. All the derivatives were thermally stable upto （1904- 10）℃ and degradation occurred after that.

Electronic Absorption Spectroscopy of H2X （X=O, Te, Po）： Theoretical Treatment of Spin-Orbit Effects

The electronic spectroscopy of H2X （X=O, Te, Po） was investigated by means of spinorbit configuration interaction （EPCISO） and restricted active space state interaction （SORASSI）. The transition energies to the low-lying singlet and triplet states of H2O, in which the SO interaction is zero, compare rather well with the experimental data as well as to other theoretical values. The theoretical electronic absorption spectrum is characterized by three allowed transitions A^1B1 （2px（O）→σ^＊g/3s（O））, B^1A1（σg→σ^＊g/3s（O）） and A^1S2（σg→σ^＊u） calculated at 7.68, 9.94, and 11.72 eV, respectively. The theoretical absorption spectra of H2X （X=Te, Po） are shifted to the red with the A^1B1 （npx（X）→σ^＊g） states calculated at 5.06 eV （H2Te） and 4.40 eV （H2Po） and the A^1B2 （σg→σ^＊u） states calculated at 7.89 eV （H2Te） and 7.77 eV （H2Po）. The largest SO splitting amounts to 0.34 eV and is found for the lowest a^3A1 of H2Po. In H2Te the SO effects are still negligible with a maximum splitting of 0.04 eV for the lowest a^3B2. The two methods lead to comparable results but the EPCISO approach depends strongly on the reference wavefunction.

Electronic structure of the rare-earth superstoichiometric dihydride GdH_(2.25)

With the WIEN2 k simulation code,ab initio calculations of electronic structure and of equilibrium properties for the superstoichiometric rare-earth dihydride GdH_(2.25)using the full-potential linearized augmented plane-wave(FP-LAPW)method within density functional theory(DFT)in generalized gradient approximation(GGA)were performed.The lattice parameter,bulk modulus,pressure derivative,density of states(DOS)and energy band structures were determined.The GGA-optimized lattice parameter agrees much better with the experimental findings than the local density approximation(LDA)one.The non-negligible electronic DOS at Fermi level confirms that GdH_(2.25)has a metallic character.The Fermi energy(E_(F))falls at a level where most of the states are rare-earth 5 d conduction states while negligible contributions of both interstitial(tetrahedral and octahedral)H s states are observed near EF.It is found that hybridization exists between s electronic orbital of both interstitial H atoms and d electronic orbitals of Gd.

First-principles study of the electronic structure of a superstoichiometric rare earth dihydride GdH2.25

We performed ab initio calculations of electronic structure and equilibrium properties for the rare earth superstoichiometric dihydride GdH2.25 （with the space group Pm-3m （No. 221）） using the full-potential linearized augmented plane wave method （FP-LAPW） approach within the density functional theory （DFT） in the generalized gradient approximation （GGA） and local density approximation （LDA） as implemented in the WIEN2k simulation code at 0 K. The equilibrium properties were determined, the density of states, electronic density and the energy band structures were studied in details. It was concluded that the GGA optimized lattice parameter agreed much better with the experimental findings than the LDA one, The non negligible electronic density of states at the Fermi level confirmed that the GdH2.25 had a metallic character. The Fermi energy EF fell at a level where most of the states were rare-earth 5d-eg conduction states while negligible contributions of both interstitial （tetrahedral and octahedral） H s-states were observed near EF, From electronic density, the bonding between Gd and tetrahedral H atoms was of prominent covalency, while was ionic between Gd and octahedral H atoms.

STUDIES ON cis-trans-ISOMERIZATION AND REACTION KINETICS OF A μ, η~2-VINYL LIGAND IN A TRIOSMIUM CLUSTER

The dihydride cluster H_2O_(s_3)(CO)_(10) reacts with ethyne to give a cis-adduct [O_(s_3)H(μ,η~2-CH=CH_2)(CO)_(10)]. The high deuterated cluster D_2O_(s_3)(CO)_(10), the reaction of D_2O_(s_3)(CO)_(10)with ethyne C_2H_2 to form the vinyl product cluster [O_(s_3)D(μ, η~2-CH=CHD)(CO)_(10)], and thereaction of H_2O_(s_3)(CO)_(10) with the deuterated ethyne C_2D_2 to form [O_(s_3)H(μ,η~2-CD=CDH)(CO)_(10)] have been reported primarily in this paper. The two cis-adducts undergo cis-trans-isomerization of μ,η~2-vinyl ligands under a small amount of the nucleophile pyridine. Usingthe combination of deuteration and dynamic ~1H,~2H NMR spectra, we report the experimen-tal evidence determined by the dynamic ~1H, ~2H NMR spectra, mechanism, and kinetic dataof the isomerization.