SCF MS Xα molecular orbital calculations are reported for the bis(η6-benzene)- and bis(η6-naphthalene)chromium(0) complexes. The bonding may be essentially discussed in terms of the covalent interactions between the metal 3d and ligand π and π* orbitals. The different charges on chromium atom in the two systems are explained by the different balances between ligand-to-metal (bonding) and metal-to-ligand (back-bonding) electron donations. Some resemblances are found between the electronic structures of the two compounds and it is possible to correlate to a large extent the energy levels of their molecular orbitals. However, a shift towards lower values is predicted for the energy levels of the naphthalene complex, together with a large disruption of all the virtual π* and 3d* levels. This would undoubtedly favor nucleophilic attack followed by metal–ring or carbon–carbon bond cleavage, in agreement with the extreme lability of the coordinated arene rings observed in this complex.
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Weber et al. (1985) studied this question.