Effective core potential oxidative addition

Representative work T. R. Cundari, ]. Am. Chem. Soc., 116, 340 (1994). Calculation of a Methane C—H Oxidative Addition Trajectory Comparison to Experiment and Methane Activation by High-Valent Complexes. M. T. Benson, T. R. Cundari, S. J. Lim, H. D. Nguyen, and K. Pierce-Beaver, /. Am. Chem. Soc., 116, 3955 (1994). An Effective Core Potential Study of Transition-Metal Chalcogenides. 1. Molecular Structure. T. R. Cundari,... 

The electron density i/ (0)p at the nucleus primarily originates from the ability of s-electrons to penetrate the nucleus. The core-shell Is and 2s electrons make by far the major contributions. Valence orbitals of p-, d-, or/-character, in contrast, have nodes at r = 0 and cannot contribute to iA(0)p except for minor relativistic contributions of p-electrons. Nevertheless, the isomer shift is found to depend on various chemical parameters, of which the oxidation state as given by the number of valence electrons in p-, or d-, or /-orbitals of the Mossbauer atom is most important. In general, the effect is explained by the contraction of inner 5-orbitals due to shielding of the nuclear potential by the electron charge in the valence shell. In addition to this indirect effect, a direct contribution to the isomer shift arises from valence 5-orbitals due to their participation in the formation of molecular orbitals (MOs). It will be shown in Chap. 5 that the latter issue plays a decisive role. In the following section, an overview of experimental observations will be presented. 

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