摘要：

A detailed construction of the frontier orbitals of M(CO)3 and M(benzene) fragments leads to a general analysis of M(CO)3 and M(CH)n, n = 3-8. The number, symmetry properties, energy, and extent in space of these frontier orbitals determine their interaction with other ligands completing the metal coordination sphere. An overlap analysis of the bonding capabilities of M(CO)3, M(benzene), and M(cyclopentadienyl) leads to the conclusion that in interaction with another metal M(C6H6) or MCp has a stronger σ interaction, but M(CO)3 is better at π bonding. In interaction with a main-group probe oxidation state effects appear to dominate. Structural information on pertinent replacement pairs is surveyed to evaluate the validity of these theoretical conclusions. The bending of hydrogens out of the carbon plane in M(CH)n complexes is traced to π interactions and a reorientation of the ring π orbitals for better overlap. The result is bending toward the metal for large n and away from the metal for small n. Pyramidality deformations in M(CO)nLm are predicted in response to the donor capability of L.

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