Fingers on the pulse: An NMR pulse scheme that provides full sensitivity in homodecoupled band‐selective NMR spectroscopy experiments is proposed (see figure). The easy implementation of this HOBS scheme as a general building block into a great variety of multidimensional NMR experiments leads to pure‐shift spectra with enhanced resolution and with the maximum attainable sensitivity.
Various ligands not forming monometallic complexes were
used for
Ru nanoparticle stabilization, enabling the control of size, shape,
and electronic properties. HRMAS NMR spectroscopy allowed us to study
surface-bound molecules, evidencing ligand hydrogenation and decomposition
of THFduring the RuNP synthesis. Catalysis studies underscore the
importance of the nature of the ligands. The RuNPs were tested in
the hydrogenation of aromatics, showing very high activities (TOF
> 60 000 h–1, 40 bar, 393 K). A pronounced
ligand effect was found, and dialkylaryl phosphine ligands gave the
fastest catalyst.
The hydrogen absorption mechanism of the 2NaH + MgB 2 system has been investigated in detail. Depending on the applied hydrogen pressure, different intermediate phases are observed. In the case of absorption measurements performed under 50 bar of hydrogen pressure, NaBH 4 is found not to be formed directly. Instead, first an unknown phase is formed, followed upon further heating by the formation of NaMgH 3 and a NaH-NaBH 4 molten salt mixture; only at the end after heating to 380 °C do the reflections of the crystalline NaBH 4 appear. In contrast, measurements performed at lower hydrogen pressure (5 bar of H 2 ), but under the same temperature conditions, demonstrate that the synthesis of NaBH 4 is possible without occurrence of the unknown phase and of NaMgH 3 . This indicates that the reaction path can be tuned by the applied hydrogen pressure. The formation of a NaH-NaBH 4 molten salt mixture is observed also for the measurement performed under 5 bar of hydrogen pressure with the formation of free Mg. However, under this pressure condition the formation of crystalline NaBH 4 is observed only during cooling at 367 °C. For none of the applied experimental conditions has it been possible to achieve the theoretical gravimetric hydrogen capacity of 7.8 wt %.
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