Overlap axial

The combination of two carbon atoms, for example in ethane, results from the axial overlap of two sp3 atomic orbitals, one from each... 

Two types of interactions are often distinguished cr interactions, which concern an axial orbital overlap, and tt interactions, where the orbital overlap occurs laterally, or sideways . These two types of overlap are illustrated in 1-24 and 1-25, respectively, for two p orbitals whose axes of revolution are either co-linear (axial overlap) or parallel (sideways overlap). Notice that another way to characterize rr interactions is to observe that the orbitals involved share a common nodal plane (P, 1-25). 

In general, a interactions are stronger than tt interactions, since axial overlap is more efficient than sideways overlap. The energy separation between the resulting orbitals is therefore larger fora (bonding) and a (antibonding) MO than for the tt and jt MO. 

We shall consider the interactions between the d orbitals on two metallic centres, initially ignoring any influence of the ligands on these orbitals. Each interaction leads to the formation of a bonding and an antibonding MO, but only the first of these, written is shown in 4-45. The interaction between the orbitals (4-45a) is of ct type the axial overlap between the two orbitals has cylindrical symmetry around the intemudear axis (z). The MO and yz (4-45b) have the same characteristics as the 7T orbitals of acetylene (4-44) they are bonding, and they possess a nodal plane that passes through the nuclei. 

The overlaps involved depend on the type of interaction. The axial overlap Sa is larger than or comparable to the lateral overlaps S -. However, the Ss overlap is much smaller than these, only about a third or a quarter of Sjt ... 

This bond is formed by the axial overlap of atomic orbitals. This bond is formed by the sideways overlap of atomic orbitals. 

The electron cloud formed by axial overlap is symmetrical about the inter-nuclear axis and consists of a single electron cloud. The electron cloud is discontinuous and consists of two charged electron clouds above and below the plane of the atoms. 

Figure 14.66 Energy diagram for the formation of a and a orbitals from the axial overlap of a a Is and 2p orbital and b two 2p orbitals... 

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