N Bonding molecular orbitals

The double bond shown in different locations in the two resonance stmctures represents a pair of electrons in a delocalized n bonding molecular orbital that spans all three of the oxygen atoms, as shown in Figure I0-37a. One lone pair also appears in different positions in the two resonance stmctures, again signaling a delocalized orbital. This lone pair is spread over both outer atoms but not across the inner atom, as shown in Figure I0-37Z>. This is a nonbonding molecular orbital,. The lone pair shown in different positions in the resonance stmctures occupies the delocalized orbital. 

Molecular orbital calculations snggest that the jr electrons in naphthalene are delocalized over the two rings and this results in substantial stabilization. These molecules are planar, and all p orbitals are suitably aligned for overlap to form n bonding molecular orbitals. Although we can draw Kekule structures for these compounds, it is strictly incorrect to use the circle in hexagon notation since the circle represents six jr electrons. Naphthalene has 10 carbons, and therefore 10 jr electrons, and anthracene has 14 jr electrons. The circle notation suggests 12 or... 

One minor complication that you should be aware of is that the relative energies of the a and n bonding molecular orbitals are reversed in some of the second-row diatomics. However, the order in which these two orbitals are filled has no effect on the predicted bond orders, so there is ordinarily no need to know which molecules follow which scheme. 

Fig. 20.4. A schematic representation of some non-bonding and n -bonding molecular orbitals in SO3 or NO3. Left the three essentially non-bonding a molecular orbitals formed by linear combinations of oxygenp orbitals in the molecular plane. In SO3 these orbital are completely filled by six electrons, in NO3 the highest, non-degenerate orbital contains a single electron. Right the four n molecular orbitals formed by linear combination of the valence shell AOs of the four atoms.

Divalent late transition metals like cobalt (d ), nickel (d ), and copper (d ) in the first row of the d-block can use five 3d orbitals, one 4s orbital, and three 4p orbitals to form 4-, 5-, or 6-coordinate complexes. As a general rule, if there are N ligands in the first-shell coordination sphere of a transition metal complex, then there should be N bonding molecular orbitals, N anti-bonding molecular orbitals, and 9-N nonbonding molecular orbitals. Exceptions to this rule occur in some square-planar complexes in which three orbitals with the same symmetry properties overlap and form chemical bonds. Usually, some coordination sites in the first-shell of the... 

Fig. 10.5 A qualitative c + n bonding molecular orbital energy level diagram for Cr(C0)6 based on Figs. 6.11 and 6.16(c) together with the associated discussion. This schematic diagram may be compared with Fig. 10.10 which is a more accurate molecular ener level diagram for Cr(C0)6.

When two p orbitals of similar phase overlap side-by-side, a n bonding molecular orbital results. 

Figure 14-1 Generation of increased-valence structures for FNO2, NO2, F2SO and O3 from Lewis structures by delocalizing lone-pair electrons into vacant antibonding molecular orbitals. (In structure (9), an oxygen electron of the NO is delocalized into an O-N bonding molecular orbital.)...

Figure 1.24 How two isolated carbon p orbitals combine to form two n (pi) molecular orbitals. The bonding MO is of lower energy. The higher energy antibonding MO contains an additional node. (Both orbitals have a node in the plane containing the C and H atoms.)...

The 7i bonding molecular orbital of formaldehyde (HCHO). The electron pair of the n bond occupies both lobes. 

The diagram shows that the six n-electrons fill the three bonding molecular orbitals for the n-system. Keep in mind that the ensemble of 7i-molecular orbitals is superimposed on the sp2 framework for the molecule. 

As we have already seen, two molecular orbitals form when two atomic orbitals overlap - a bonding molecular orbital and an antibonding molecular orbital. End-on overlap of atomic orbitals along the axis of the bond results In cr and cr molecular orbitals forming. Slde-on overlap of atomic orbitals at an angle perpendicular to the axis of the bond results In the formation of n and molecular orbitals. 

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