Phase separation in hydrides of Zr2Ni

Room temperature X-ray and Mössbauer measurements show three single phase fields for hydrogen concentrations up to Zr₂NiH_5.1. Narrow two phase regions exist around Zr₂NiH_4.1 and between Zr₂NiH_4.9 and Zr₂NiH_5.1. Hydrogen effusion curves at constant pressure indicate two different desorption stages with activation energies of 50 kJ (mol H₂)^?1 and 110 kJ(mol H₂)^?1 which are in general agreement with theoretical values.     

Hydrogenation of Zr2Ni

The intermetallic compound Zr₂Ni has been found to take up hydrogen on charging at room temperature. Zr₂(NiFe) H_4.7 and Zr₂(NiFe) H_4.5 show the same structure (CuAl₂ type) as the uncharged compound but with an expanded lattice.Analysis of room temperature spectra in zero and applied fields indicates that the⁵⁷Fe atoms occupy Ni sites in Zr₂(Ni ⁵⁷Fe). Volume expansion effects account for about one third of the increase in isomer shift ( +0.58 mms^–1) observed on hydrogenation. The distribution of hydrogen atoms around the probe³⁷Fe atoms also causes a decrease of 0.23 mms^–1 in the mean value for the quadrupole splitting compared Rith uncharged Zr₂Ni.     

Synthesis of mono- and polyhydroxylated cyclobutane nucleoside analogs

Enantiomerically enriched cyclobutene compounds 13 and 24 are good precursors of several cyclobutane nucleoside analogs. The synthetic ways involve, in the key step, either hydroboration or dihydroxylation.     

Relaxation rates and diffusion in hybrides of Zr2Ni

Proton spin-spin and rotating frame spin-lattice relaxation in Zn₂Ni hydrides have been investigated. Activation energies for hydrogen motion were determined from Arrhenius plots of the relaxation times and found to be in general agreement with earlier NMR and PAC works. In common with previous studies of hydrides, asymmetric slopes about the relaxation minima are observed as well as adeviation from the motional narrowing behaviour at high temperatures.