Pincer-ligated iridium complexes have proven to be highly effective catalysts for the dehydrogenation and transfer-dehydrogenation of al-A C H T U N G T R E N N U N G kanes. Immobilization onto a solid support offers significant potential advantages in the application of such catalysts particularly with respect to catalyst separation and recycling. We describe three approaches toward such immobilization: (i) covalent attachment to a Merrifield resin, (ii) covalent bonding to silica via a pendant alkoxysilane group, and (iii) adsorption on g-alumina (g-Al 2 O 3 ), through basic functional groups on the para-position of the pincer ligand. The simplest of these approaches, adsorption on g-Al 2 O 3 , is also found to be the most effective, yielding catalysts that are robust, recyclable, and comparable to or even more active than the corresponding species in solution. Spectroscopic evidence (NMR, IR) and studies of catalytic activity support the hypothesis that binding occurs at the para-substituent and that this has only a relatively subtle and indirect influence on catalytic behavior.
The decay rate of 7 Be has always been measured by either forming a beryllium compound or implanting 7 Be in a medium. We can quantitatively understand the measured changes of 7 Be decay rates in different environments as well as its L/K orbital electron capture ratio using tight-binding linear muffin-tin orbital method calculations. We find that 7 Be loses a very substantial fraction of its 2s electrons in a medium. As a result of this loss of 2s electrons, the extracted nuclear matrix element of the 7 Be electron capture reaction from terrestrial decay rate measurements should increase by 2-2.7%, thus decreasing the calculated 8 B solar neutrino flux from the Standard Solar Model by 2-2.7%.
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