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Author Topic: Carbon monoxide: HOMO  (Read 5551 times)

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Winga

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Carbon monoxide: HOMO
« on: February 14, 2006, 12:00:21 AM »

According to my two lecture notes, one said the HOMO of CO is a sigma "bonding" orbital formed by C's 2p and O's 2p orbitals (e.g. both are 2px orbitals). While another one said the HOMO is a sigma "antibonding" orbital formed by C's 2s and O's 2s orbitals.

So, which one is correct? (or which one is more preferable?)
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Mitch

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Re:Carbon monoxide: HOMO
« Reply #1 on: February 14, 2006, 12:31:21 AM »

The answer to every inorganic question you have asked here is in this book. You should buy it and read it. http://www.amazon.com/gp/product/093570261X/qid=1139916554/sr=1-7/ref=sr_1_7/002-3684750-5645629?s=books&v=glance&n=283155
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Albert

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Re:Carbon monoxide: HOMO
« Reply #2 on: February 14, 2006, 12:49:14 AM »

According to my two lecture notes, one said the HOMO of CO is a sigma "bonding" orbital formed by C's 2p and O's 2p orbitals (e.g. both are 2px orbitals). While another one said the HOMO is a sigma "antibonding" orbital formed by C's 2s and O's 2s orbitals.

So, which one is correct? (or which one is more preferable?)

In my opinion, the former is the correct one.
« Last Edit: February 14, 2006, 01:23:47 AM by Albert »
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Winga

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Re:Carbon monoxide: HOMO
« Reply #3 on: February 14, 2006, 10:53:06 PM »

The energy level of C's and O's atomic orbitals in this diagram are quite similar.

But another one shows that the energy difference is quite large that gives another pattern.

As you know, it is due to electronegative difference between C and O, but in what extent?
If small, properly, it's just same as your case, if large, it will be another case.
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Albert

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Re:Carbon monoxide: HOMO
« Reply #4 on: February 15, 2006, 12:06:05 AM »

Carbon and oxygen belong to the same period and are quite close to each other.
According to that, I'd say their atomic orbitals have similar energies.
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Winga

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Re:Carbon monoxide: HOMO
« Reply #5 on: February 15, 2006, 02:03:57 AM »

Here is another version...
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Winga

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Re:Carbon monoxide: HOMO
« Reply #6 on: February 15, 2006, 02:12:49 AM »

After comparing them, I drew a conclusion...

If CO ligand donates e- density to metal centre through sigma bonding (from sigma* orbital), the bond order of CO will greater than 3 (neglect back pi bonding).

I have never heard about such a bond order of CO, I think yours is correct.
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