Theoretical Investigations on How to Reproduce d-[pi] Bonds: Transition-Metal Cation-Benzene Complex Calculations

• Published in: Bulletin of the Chemical Society of Japan Vol. 82; no. 11; pp. 1367 - 1371
• Main Authors: Tsuneda, Takao, Hirosawa, Tsuyoshi, Nakatsuka, Yutaka, Hirao, Kimihiko
• Format: Journal Article
• Language: English
• Published: 01.01.2009
• Subjects: Binding energy; Cations; Chemical bonds; Correlation; Density functional theory; Functionals; Mathematical analysis; Transition metals
• ISSN: 1348-0634
• DOI: 10.1246/bcsj.82.1367

Reproducibilities of d-[pi] bonds were investigated on calculating complexes of first-row transition-metal cation (M super(+)) and benzene (Bz). Calculations were carried out for half-sandwich MBz super(+) and sandwich MBz sub(2) super(+) complexes with several types of density functional theories (DFTs) and single-configurational wave function theories (WFTs). As a result, it was concluded that electron correlations are required to give the binding energies of d-[pi] bonds even qualitatively, and DFTs would reproduce d-[pi] bonds with quantitative accuracies only if electron correlations and long-range exchange interactions were both taken into consideration in exchange-correlation functionals used. In MBz super(+) calculations, WFTs fairly underestimated the binding energies for early transition metals (M = Sc-Cr) because of multiconfigurational effects. In contrast, DFTs overestimated them for late transition metals (M = Fe-Cu) due to insufficient long-range interactions in exchange functionals. For MBz sub(2) super(+), DFTs and WFTs gave similar binding energies for MBz sub(2) super(+), although WFTs slightly overestimated them for late transition metals. Furthermore, it was suggested that the experimental binding energies of CrBz sub(2) super(+) and MnBz sub(2) super(+) are probably misestimated.