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Topic: organometallic complexes- bond lengths and geometric isomerism  (Read 4036 times)

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Offline missUK11

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Hello all,

I am having a little trouble with the question below. I have used the estimated standard deviations in brackets to determine which V-O bonds are statistically different but I don't know how to assign the oxygen atoms to the correct positions in the metal's octahedral coordination sphere.

Many thanks in advance.

Question

The ion [V(O)(H2O)5]2+ is characterized in an X-ray crystallographic experiment
as exhibiting six vanadium-oxygen bond lengths (Å).

V-O(l) 2.103(8 ) 
V-O(2) 2.126(9)
V-O(3) 2.249(8 )
V-O(4) 1.848(9)
 V-O(5) 2.085(9)
V-O(6) 2.154(9)

Comment on these bond lengths and assign the oxygen atoms to the correct
positions in the metal's octahedral coordination sphere, providing an explanation
for the placement of each oxygen atom. Comment on the bonding of the ligands
to the vanadium.


Offline Archer

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Re: organometallic complexes- bond lengths and geometric isomerism
« Reply #1 on: April 17, 2014, 08:24:45 PM »
Hello all,

I am having a little trouble with the question below. I have used the estimated standard deviations in brackets to determine which V-O bonds are statistically different but I don't know how to assign the oxygen atoms to the correct positions in the metal's octahedral coordination sphere.

Many thanks in advance.

Question

The ion [V(O)(H2O)5]2+ is characterized in an X-ray crystallographic experiment
as exhibiting six vanadium-oxygen bond lengths (Å).

V-O(l) 2.103(8 ) 
V-O(2) 2.126(9)
V-O(3) 2.249(8 )
V-O(4) 1.848(9)
 V-O(5) 2.085(9)
V-O(6) 2.154(9)

Comment on these bond lengths and assign the oxygen atoms to the correct
positions in the metal's octahedral coordination sphere, providing an explanation
for the placement of each oxygen atom. Comment on the bonding of the ligands
to the vanadium.



Show us what you have done so far with your calculations, I can see two bond lengths which stand out from the rest
« Last Edit: April 17, 2014, 08:47:52 PM by Archer »
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Offline missUK11

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Re: organometallic complexes- bond lengths and geometric isomerism
« Reply #2 on: April 18, 2014, 06:17:05 AM »
Hello all,

I am having a little trouble with the question below. I have used the estimated standard deviations in brackets to determine which V-O bonds are statistically different but I don't know how to assign the oxygen atoms to the correct positions in the metal's octahedral coordination sphere.

Many thanks in advance.

Question

The ion [V(O)(H2O)5]2+ is characterized in an X-ray crystallographic experiment
as exhibiting six vanadium-oxygen bond lengths (Å).

V-O(l) 2.103(8 ) 
V-O(2) 2.126(9)
V-O(3) 2.249(8 )
V-O(4) 1.848(9)
 V-O(5) 2.085(9)
V-O(6) 2.154(9)

Comment on these bond lengths and assign the oxygen atoms to the correct
positions in the metal's octahedral coordination sphere, providing an explanation
for the placement of each oxygen atom. Comment on the bonding of the ligands
to the vanadium.



Show us what you have done so far with your calculations, I can see two bond lengths which stand out from the rest

For each V-O bond I was first advised to work out a range of : length ± 3σ to determine which bonds are statistically significantly different by comparing the bonds pairwise.

So worked out that:

V-O(1) and V-O (2) are indistinguishable
V-O (1) and V-O(3) are distinguishable
V-O (1) and V-O (4) are distinguishable
V-O (1) and V-O (5) are indistinguishable
V-O (1) and V-O (6) are distinguishable
V-O (2) and V-O(3) are distinguishable
V-O (2) and V-O (4) are distinguishable
V-O (2) and V-O(5) are distinguishable
V-O (2) and V-O (6) are distinguishable
V-O (3) and V-O (4) are distinguishable
V-O (3) and V-O(5) are distinguishable
V-O (3) and V-O (6) are distinguishable
V-O (4) and V-O(5) are distinguishable
V-O (4) and V-O (6) are distinguishable
V-O (5) and V-O (6) are distinguishable

So there are only two pairs of bonds that are not statistically significantly different. So how can I use that information to assign the oxygen atoms to the correct positions in the metal's octahedral coordination sphere?

Thanks!

Offline Archer

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Re: organometallic complexes- bond lengths and geometric isomerism
« Reply #3 on: April 18, 2014, 10:22:10 AM »
Quote
The ion [V(O)(H2O)5]2+ is characterized in an X-ray crystallographic experiment
as exhibiting six vanadium-oxygen bond lengths (Å).
If you ignore the water molecules what sort of bonding have you got between the vanadium and the oxygen from V(O) as it's written?
“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

Offline missUK11

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Re: organometallic complexes- bond lengths and geometric isomerism
« Reply #4 on: April 18, 2014, 11:01:53 AM »
Quote
The ion [V(O)(H2O)5]2+ is characterized in an X-ray crystallographic experiment
as exhibiting six vanadium-oxygen bond lengths (Å).
If you ignore the water molecules what sort of bonding have you got between the vanadium and the oxygen from V(O) as it's written?

V=O

Offline Archer

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Re: organometallic complexes- bond lengths and geometric isomerism
« Reply #5 on: April 22, 2014, 03:09:57 PM »
Got a bit ahead of myself, can you show your calculations for the indistinguishable bonds and V-O(2) & V-O(5)
“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

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