saturated alkanes. It should be noted that in condensed phase studies at Pd(II) centers, carbonium ion intermediates have been previously proposed.46 For example, oligomerization and isomerization of olefins by Pd(CH3CN)42+ have been proposed to proceed via carbonium ion intermediates.
ConclusionThe reactivities of Ru+, Rh+, and Pd+ are shown to be remarkably different from their first-row congeners. Whereas Co+ and Ni+ dehydrogenate alkanes by a 1,4-elimination mechanism, the corresponding second-row metal ions appear to effect 1,2dehydrogenations. The reactions of Ru+ and Rh+ are characterized by C-H insertions and facile /3-H transfers. Unlike their first-row congeners, /3-methyl transfers, and C-C insertions do not occur for Ru+ and Rh+. Furthermore, the barriers for reductive elimination of RH and H2 from Rh-(olefin)+ complexes are quite small, in contrast to those proposed previously for Co+.
Thermodynamic values for the clustering reactions of carbon dioxide with Cl−, H3O+, HCO+2 , and HCO+ were measured with a pulsed electron-beam high-pressure mass spectrometer. The measured enthalpy changes are reproduced satisfactorily by the ab initio molecular orbital calculations. While Cl−(CO2)n is of the symmetric geometry, H3O+(CO2)n, HCO+2(CO2)n, and HCO+(CO2)n are of the form of the shell plus surroundings. The small fall-off of the bonding energy for the cluster growth is ascribed to the large quadrupole moment of CO2 as well as those on the shell.
When 1 Torr of methane was decomposed in a radio-frequency glow discharge plasma, ethane, ethylene, and acetylene were produced as major products. In order to determine the relative importance of radical and ionic processes for the formation of these major products, iodine and ammonia were used as radical and ion scavengers, respectively. It was found that the major products were formed mainly by radical processes and the contribution of ionic processes is within the experimental error. The mechanisms for the formation of ethane, ethylene, acetylene, and C3 ~ C4 compounds were discussed.
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