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Topic: Iron - Cyanokelate (III) ion.  (Read 5328 times)

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Offline Pero

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Iron - Cyanokelate (III) ion.
« on: February 03, 2008, 04:56:25 PM »
Hi, I am an undergraduate student of Environmental Engineering in Zagreb and I have a nice little question about a complex ion I don't quite understand.

The chemical formula of this complex ion is [Fe(CN)4]3-.

What I would like you to help me on is how are the sp3d2 hybrid molecular orbitals formed in such a compound and why are they formed in such a way that is described in the book I'm using (there are three d - orbitals of iron and six hybrid sp3d2 - orbitals with CN- ions in them)?

I must note that I have a generic knowledge in this huge course I'm taking at college and I'm quite stuck at this point.

I am very sorry that I might have not searched out the entire forum before I posted this.

Thank you in advance!

Offline Alpha-Omega

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Re: Iron - Cyanokelate (III) ion.
« Reply #1 on: February 03, 2008, 06:55:52 PM »

Fe has what is called dsp hybridization/bonding.  And yes all three orbitals participate in the bonding.


Fe:  1s2 2s2 2p6 3s2 3p6 4s2 3d6

For Fe we can write Fe:  1s2 2s2 2p6 3s2 3p6 3d6 4s2 

Fe3+:  [Ar]3d6

Fe2+: [Ar]3d5

So for Fe we have 3s2 3p6 3d6

Fe forms d2sp3 Hybrids

These particular d2sp3 hybrids are combinations of two 3d, the 3s, and three 3p functions.

The 3s :  3 is the energy level, S is the subshell, 1 orbital

The 3p:  3 is the energy, p is the subshell, 3 orbitals px, py, and pz

The 3d:  3 is the energy, d is the subshell, 5 orbitals dyz, dxz, dxy, dx2-y2, and dz2.

In general:

S subshell has only 1 orbital.
The p subshell has 3 orbitals.
The d subshell has 5 orbitals.
The f subshell has 7 orbitals.

In Fe there are 6 electrons in the 3d shell.

Hence, the designation  d2sp3 Hybrids

For octahedral iron complexes:  There are six d2sp3 hybrid orbitals. They are arranged in an octahedral layout so that each has four other orbitals at 90° to it and one at 180°.

The following links should help you too:

http://faculty.colostate-pueblo.edu/linda.wilkes/111/3c.htm

http://winter.group.shef.ac.uk/orbitron/AO-hybrids/d2sp3/index.html

http://www.chem1.com/acad/webtext/chembond/cb09.html

http://www.chemguide.co.uk/inorganic/complexions/whatis.html



« Last Edit: February 03, 2008, 07:42:33 PM by Alpha-Omega »

Offline Pero

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Re: Iron - Cyanokelate (III) ion.
« Reply #2 on: February 04, 2008, 02:31:20 AM »
Thank you very much, you've been a great help, but I already know the part with how many electrons may fit in how many orbitals!

One more question :

At homonuclear bonding of let's say for example Bohr's (B2) molecule why does pz and pz orbitals overlay after px and py overlaying? Isn't the general rule that sigma bonds get formed before pi bonds?

Thanks!

Offline Kryolith

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Re: Iron - Cyanokelate (III) ion.
« Reply #3 on: February 04, 2008, 03:24:31 AM »
Are you talking about time?  ???

Offline Alpha-Omega

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Re: Iron - Cyanokelate (III) ion.
« Reply #4 on: February 04, 2008, 07:54:48 AM »
Try these links:

http://cnx.org/content/m14777/latest/

http://www.chem1.com/acad/webtext/chembond/cb08.html

Are you asking about which bonds will form regarding overlap and symmetry..because that is what that description sounds like to me....?  Basically,  the orbitals involved in the bonding will be those which give the molecule (in terms of bonding orbitals) the lowest energy, greatest overlap and the highests degree of symmetry.
« Last Edit: February 04, 2008, 08:12:13 AM by Alpha-Omega »

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