Molecular orbital overlap diagrams

Scheme 3.2 Schematic molecular orbital overlap diagrams for metal coordination of alkynes and vinylidenes. Symmetry labels are assigned according to the symmetry of the M-L interaction.

Fig. 11. Molecular orbital energy diagram for ReH92- based on overlap considerations. (Note that the metal 6p, 5d and the ligand orbitals are degenerate sets and are separated here for clarity in showing which orbitals combine.)...

An s-orbital and a p-orbital on different atoms may overlap to form molecular orbitals. One of these interactions forms a bonding o-orbital and the other is nonbonding. Draw diagrams to represent the two types of orbital overlap that give rise to tr-bonding and nonbonding orbitals. 

Let us first briefly review the construction of molecular orbitals in simple diatomic molecules, AB, using the linear combination of atomic orbitals (LCAO) scheme. The end product for the first long row of the periodic table is the well-known diagram in Fig. 6-1. We focus on two broad principles that are exploited in the construction of this diagram one has to do with symmetry and overlap, the other concerns energies. 

A schematic molecular orbital diagram for the Fe-Fe interaction in an S = I valence-delocalized Fe Fe pair based on effective C v symmetry at the Fe sites and the observed electronic transitions for the valance-delocalized [Fe2S2l cluster is shown in Fig. 15. The dominant interaction (responsible for the S = ground state) is the a overlap between the pair of orbitals, with progressively smaller tt interactions between pairs of d z and dyz orbitals and S interactions between pairs of d y amd / orbitals. The three highest energy tran-... 

Therefore, in the final analysis, the quadruple bond consists of one a bond, two it bonds, and one S bond. The configuration in which the Cl atoms are in eclipsed positions provides maximum overlap. From the rather intuitive analysis provided here, it is possible to arrive at a qualitative molecular orbital diagram like that shown in Figure 21.23 to describe the Re-Re bond. 

A molecular orbital (MO) is an orbital resulting from the overlap and combination of atomic orbitals on different atoms. An MO and the electrons in it belong to the molecule as a whole. Molecular orbitals calculations are used to develop (1) mathematical representations of the orbital shapes, and (2) energy level diagrams for the molecules. 

Although structures involving methyl groups bonded simultaneously to two carbon atoms by means of an overlap between the hydrogen orbitals and the />-orbitals of the carbon atoms may be readily enough assimilated, the state of structural theory is such that most of the cyclic intermediate or transition state structures are dubbed non-classical. In many cases they are best depicted by molecular orbitals, usually by diagramming the component atomic orbitals in the best position for overlap. Since maximum overlap of the component atomic orbitals imposes certain geometric requirements, pre-... 

The formation of bonding molecular orbitals by an overlap of atomic orbitals applies not only to the Is orbitals of hydrogen, but also to other atomic orbitals. When the atomic orbitals overlap along the axis of the bond, a covalent bond, called a sigma (a) bond, results. This is normally referred to as end-on overlap. Some examples of the formation of a bonds from overlapping atomic orbitals are shown in the diagrams. 

In the benzene molecule, each carbon atom is sp hybridised and the three half-filled sp hybrid orbitals form a bonds with a hydrogen atom and two neighbouring carbon atoms. This leaves an electron occupying a p orbital on each carbon atom. Each of these p orbitals overlaps slde-on with p orbitals on neighbouring carbon atoms, and a tt molecular orbital Is formed, as shown in the diagram. 

Figure 3.5 Orbital envelope diagrams showing the formation of the bonding and anti-bonding molecular orbitals when two 1s atomic orbitals overlap...

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