Kepert model

Electroneutrality principle The Kepert model Coordination numbers Isomerism... 

The Kepert model rationalizes the shapes of <5 -block metal complexes [ML ], [ML ] or [ML ] by considering the repulsions between the groups L. Lone pairs of electrons are ignored. For coordination numbers between 2 and 6, the following arrangements of donor atoms are predicted ... 

Table 19.4 lists coordination environments associated with coordination numbers between 2 and 9 not all are predictable using the Kepert model. For example, after considering the repulsions between the cyano ligands in [Cu(CN)3] , the coordination sphere would be predicted to be trigonal planar (19.2). Indeed, this is what is found experimentally. The other option in Table 19.4 is trigonal pyramidal, but this does not minimize interligand repulsions. One of the most important classes of structure for which the Kepert model does not predict the correct answer is that of the square planar complex, and here electronic effects are usually the controlling factor, as we discuss in Section... 

Another factor that may lead to a breakdown of the Kepert model is the inherent constraint of a ligand. For example ... 

Within the Kepert model, what geometries do you associate with the following coordination numbers ... 

We turn instead to the Kepert model, in which the metal lies at the centre of a sphere and the ligands are free to move over the surface of the sphere. The hgands are considered to repel one another in a similar manner to the point charges in the VSEPR model. However, imlike the VSEPR model, that of Kepert ignores non-bonding electrons. Thus, the coordination geometry of a J-block species... 

The coordination number of a compound is defined as the number of attachment sites of the various ligands to the metal center. The valence-shell electron-pair repulsion (VSEPR) model does not work well for transition compounds having partially filled d-subshells. The Kepert model is sometimes used instead. As with the VSEPR model, the metal ion is assumed to be spherical with the ligands lying along the surface of the sphere. The ligands will repel one another for either electronic or steric reasons and will tend to distribute themselves around the sphere so as to avoid each other. In the Kepert model, the lone pair electrons (which are the low-lying d-electrons in the... 

Ground state electronic configurations Physical properties Reactivity of the metals Characteristic properties Electroneutrality principle Kepert model Coordination numbers Isomerism... 

---