Activation of alkanes by ruthenium, rhodium, and palladium ions in the gas phase: striking differences in reactivity of first- and second-row metal ions

Journal Article · Wed Sep 17 00:00:00 EDT 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00279a003· OSTI ID:5344957

Tolbert, M A; Mandich, M L; Halle, L F; Beauchamp, J L

The reactions of Ru/sup +/, Rh/sup +/, and Pd/sup +/ with alkanes are studied in the gas phase by using an ion beam apparatus. The reactivity of the second row group 8-10 metal ions is shown to be dramatically different than that of their first-row congeners. Studies with deuterium labeled alkanes reveal that Ru/sup +/, Rh/sup +/, and Pd/sup +/ all dehydrogenate alkanes by a 1,2-mechanism, in contrast to the 1,4-mechanism of Co/sup +/ and Ni/sup +/ and the combination of 1,2- and 1,4-processes for Fe/sup +/. In most respects, Ru/sup +/ and Rh/sup +/ exhibit similar reactivity quite distinct from that observed for Pd/sup +/. The reactions of Ru/sup +/ and Rh/sup +/ are dominated by the loss of one or more molecules of hydrogen, via mechanisms characterized by C-H bond insertions and ..beta..-H transfers. In contrast to the reactions of their first-row congeners, neither ..beta..-methyl transfers nor C-C bond insertions occur competitively at Ru/sup +/ and Rh/sup +/ centers. Furthermore, evidence is presented which indicates that the barriers for reductive elimination of H/sub 2/ and HR from Rh-(olefin)/sup +/ complexes are much smaller than the corresponding barriers for the first row group 8-10 metal ions. These low barriers may result in the formation of internally excited products able to undergo a second exothermic elimination reaction. The differences in reactivity of the first and second row group 8 and 9 metal ions are proposed to be due to differences in the sizes and shapes of the orbitals used for bonding. Although the reactivity of Pd/sup +/ appears in some ways to be quite similar to that of Ni/sup +/, the mechanism by which alkanes are activated by Pd/sup +/ may be quite different than for any of the first-row metal ions.

• Research Organization: California Institute of Technology, Pasadena
• OSTI ID: 5344957
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:19; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ALKANES
CATIONS
CHARGED PARTICLES
CHEMICAL BONDS
CHEMICAL REACTIONS
COLLISIONS
DATA
DEUTERIUM
ELEMENTS
EXPERIMENTAL DATA
HYDROCARBONS
HYDROGEN ISOTOPES
INFORMATION
ION COLLISIONS
ION-MOLECULE COLLISIONS
IONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
METALS
MOLECULE COLLISIONS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PALLADIUM
PLATINUM METALS
RHODIUM
RUTHENIUM
STABLE ISOTOPES
TRANSITION ELEMENTS