| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1997: ¥2,600,000 (Direct Cost: ¥2,600,000)
|
|---|
| Research Abstract |
Variable temperature, MAS and wide-line solid state NMR measurements have been carried out on H_4Ru_4(CO)_<12> and H_4Ru_4(CO)_<12>{P(OMe)_3}. The variation of spin-lattice relaxation time (Ti) and linewidth at half intensity (DELTAupsilonl/2) of the hydride resonance with temperature for both samples are very similar and suggests that a common hydride movement occurs with Ealpha=17 * 2 LI mo1^<-1>. We attribute this movement to a 2-site H-flip about H-occupied Ru-Ru edges which preserves the site symmetry of the crystals.
The molecular structures of(NMe_4)4-x[H_xNi_<12>(CO) _<21>].S (x=1, S=Me2CO ; x=2, S=1/2 THF) are reported. Both anions are similar and consist of a central Ni_6(CO)_3(mu-CO)_6 - layer flanked on both sides by two Ni_3(CO)_3(mu-CO)_3-layers such that the Ni_<12>-fragrpent is hexagonal close-packed. The separation between the central Ni_6-plane (B) and the two outer Ni_3-planes (A, C) is consistent with H-occupancy of either one (x=1) or both (x=2) of the two octahedra
… More
l metal cavities. Variable temperature solid state ^1H MAS and ^<13>C CP/MAS NMR spectra are reported for both clusters. For the dihydride, the solid state ^1H and ^<13>C NMR spectra remain unchanged from low to room temperature and are consistent with the X-ray structure ; at room temperature, there are two hydride resonances consistent with them being on the plane of symmetry on opposite sides of the Ni_6-layer and the highfield shift is consistent with them not being in the center of the Ni_6- octahedral cavity. For [H_2Ni_<12>(CO)_<12>]^<2->, there is close agreement between the solution and solid state ^<13>CO chemical shifts except for the inner bridging carbonyls which appear in solution as one resonance whereas in the solid state occur as two resonances due to the bridging CO's being either above or below the Ni6-plane. At higher temperatures, there is evidence for H-movement (probably oscillation about the plane of symmetry) but ^<13>C spectra indicate that the CO's remain essentially static. For the monohydride, three of the bridging CO's are almost co-planar with the Ni_6-plane, one, C6, is significantly bent towards the hydride and two CO's are in intermediate positions ; the low temperature solid state ^<13>CO NMR spectra appear to be entirely consistent with this structure. At room temperature, there is some coalescence of the ^<13>CO resonances, suggesting some carbonyl-movement, but there is no evidence for H-migration from the occupied interstitial octahedral site to the unoccupied octahedral site. Less
|
