Electron Density of Transition Metal Complexes

The intermediate Hamiltonian Fock-space coupled-cluster calculations of Infante et al. [1146] were performed in an all-electron approach explicitly correlating 26 electrons and using large de ontracted basis sets. 

for the Ft complex, the scalar-relativistic DKH Hamiltonian and the spin-orbit ZORA-Hamiltonian recover relativistic effects on the electron density of the valence region found in four-component calculations. This is particularly remarkable since the DKH density has not been corrected for the picture-change error in these calculations. The difference density maps for the Ft complex clearly show the importance of the scalar-relativistic contraction of the inner shells, while spin-orbit effects can be neglected for this closed-shell complex (otherwise, the DKH results would deviate much more from the four omponent and ZORA data). In the case of the Ni system the spin-orbit-coupling-induced splitting of the d shell is small but noticeable. 

Knowledge of the accurate electron density is decisive especially for the development of chemical concepts that are based on the analysis of this observable. Such concepts are Gillespie s valence-shell electron-pair repulsion model [1149] or the ligand-induced charge concentrations [880,1150-1152] that are designed to predict molecular structures and even chemical reactivity. Both approaches can be related to Bader s theory of atoms in molecules [1153], for which relativistic generalizations have been discussed in the literature [1154,1155]. 

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