摘要：

The energy ordering, symmetry, and extent in space of the valence molecular orbitals of a range of geometries of M(CO)3, M(CO)4, and M(CO)5 fragments, where M is a transition metal center, are analyzed in detail. The properties of the fragment orbitals are then used to examine the ability of the fragments to interact with other ligands as well as the geometrical preferences of the isolated fragments. The following problems are discussed: the pyramidality of five-coordinate fragments, metal-metal bond formation, seven-coordination, stabilization of "umbrella" distortions of fragments, the difference between M(CO)n fragments and MLn, with L = π donor, geometrical distortions in transition metal hydrides, why Fe(CO)3 favors bonding with conjugated dienes while Cr(CO)4 coordinates preferentially with unconjugated dienes.

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