The Covalent Bond Classification Method and Its Application to Compounds That Feature 3-Center 2-Electron Bonds

摘要

This article provides a means to classify and represent compounds that feature 3-center 2-electron (3c-2e) interactions according to whether (1) the two electrons are provided by one or by two atoms; (2) the central bridging atom provides two, one, or zero electrons; and (3) the interaction is open or closed. Class I 3c-2e bonds are defined as those in which two atoms each contribute one electron to the 3-center orbital, while Class II 3c-2e bonds are defined as systems in which the pair of electrons are provided by a single atom. The use of appropriate structure-bonding representations enables the [ML_lX_xZ_z] covalent bond classification of the element of interest to be evaluated. This approach is of considerable benefit in predicting metal-metal bond orders that are in accord with theory for dimetallic compounds that feature bridging hydride and carbonyl ligands.