Theoretical study of M+ RG2: (M+= Ca, Sr, Ba and Ra; RG= He–Rn)

Ab initio calculations were employed to investigate M+ RG2 species, where M+ = Ca, Sr, Ba and Ra and RG= He–Rn. Geometries have been optimized, and cuts through the potential energy surfaces containing each global minimum have been calculated at the MP2 level of theory, employing triple-ζ quality basis sets. The interaction energies for these complexes were calculated employing the RCCSD(T) level of theory with quadruple-ζ quality basis sets. Trends in binding energies, De, equilibrium bond lengths, Re, and bond angles are discussed and rationalized by analyzing the electronic density. Mulliken, natural population, and atoms-in-molecules (AIM) population analyses are presented. It is found that some of these complexes involving the heavier Group 2 metals are bent whereas others are linear, deviating from observations for the corresponding Be and Mg metal-containing complexes, which have all previously been found to be bent. The results are discussed in terms of orbital hybridization and the different types of interaction present in these species

KINETIC AND THERMODYNAMIC STUDIES OF GASEOUS METALLO-ORGANIC CATIONIC COMPLEXES

Author Institution: Department of Chemistry and Biochemistry, Baylor University, Waco, Texas, 76798The construction of a custom fabricated photodissociation spectrometer permits the determination of thermodynamic properties (activation energies), reaction rates, and mechanistic details of bare metal cation mediated $\sigma$-bond activation in the gas phase. Specifically, the products and rates resulting from the unimolecular decomposition of the Ni$^+$Acetaldehyde adduct are monitored after absorption of a known amount of energy. The two dissociative products which are observed in high yield are Ni$^+$ and Ni$^+$CO. The Ni$^+$CO fragment ion could result from the activation of a C-C $\sigma$-bond or from the activation of a C-H $\sigma$-bond. The rate constant for the decarbonylation of Ni$^+$Acetaldehyde was approximately 30 percent greater than that of the rate constant for the decarbonylation of Ni$^+$Acetone. For the decarbonylation of Ni$^+$Acetone, there needs to be a methide shift, whereas in the decarbonylation of Ni$^+$Acetaldehyde one could have C-C insertion followed by an aldhyde H-shift. The rate-limiting step of the decarbonylation process will be discussed