[Ifeffit] Regarding a fit for Fe(OTf)2
pushkar shejwalkar
pshejwalkar2004 at gmail.com
Wed Dec 3 23:40:07 CST 2014
Dear All (and especially B and Jason),
Thank you for your time and sorry for incomplete information.
Here is a chemistry behind Fe(OTf)2. Yes jason you are right and the Fe is
coordinate through O. I tried to look into the crystal structure of
Fe(OTf)2 (which is Fe(-OS(=O)2CF3) and there are two crystal structure
available where water is coordinated to Fe (octahedral) and
acetonitrile(ACN) (octahedral). Thus if the triflate is present it is
second shell S-scatterer. However, in case of ACN crystal, triflate is
coordinated to Fe and rest four are ACN molecules. in my case, I was
expecting that Fe(OTf)2 with no ligand (which after the suggestion from
Chemist that Jason met), doesn't seems to be possible. So now I am thinking
that the rest may be water molecules. BUT then the question is
ARE WATER MOLECULES NOT DIFFERENT THAN THE TRIFLATE ANION in terms of bond
length? The analysis and the reliability of the structure is more difficult
because other possible structural arrangement using different configuration
(such as 4 H2O and two triflate in this case) for which the crystal data is
not avaialble.
Few other information to answer some of the Bruce's question.
The XRF does show that there is S in the sample, However the calibration
was not performed (so I dont know how much Fe:S ratio in molar terms) but
qualitatively speaking there is enough S.
I am not sure about the stability of the sample under X-ray beam, but I do
not expect it to be reactive (but tht doesnt mean anything).
Even if the Fe(OTf)2 is hygroscopic, my basic knowledge of chemistry will
tell me that unless the sample was suspended in water or ACN the
replacement of all the triflates with Solvent molecules will be
thermodynamically difficult process. Yes coordination of (upto) 4 solvent
molecules is very easy to make octahedrally stable structure in solid state.
Also I am using the Fe(OTf)2 with BN and the concentration of Fe(OTf)2
seems to be pretty good, The edge jump of about 1.0 was observed and with
this I think we can say that Fe is present in sufficient quantity.
So in order to summarize, if I dont have crystal structure, can I still
make the fit using all (6) oxygens, but 4 with one bond length and other
two with other bond length? although the bond distances will not be
extremely different( may be a difference of about 0.2 angstrom). Is that
resolvable? and this is the other reason why I was little concern about the
S because it may give me an additional point to defend my structure if I
can show Fe-S path. Would you expect the S to show peak in R space?
Once again thank you all for actively participating in solving my problem,
I will keep you guys updated as I discover/research more into the structure
and analysis of catalysts center.
Best
Pushkar
On Thu, Dec 4, 2014 at 6:37 AM, Jason Gaudet <jason.r.gaudet at gmail.com>
wrote:
> So I did in fact run into an actual chemist with actual experience on this
> material not ten minutes ago, and she explained the structure is Fe hydride
> cations and triflate anions; without the water there is no structure. You
> can presumably replace water with ACN or something similar and get the same
> general structure, but if you took iron (II) triflate hexahydrate and
> attempted to remove water without substitution, you would've probably made
> iron nanoparticles or some other material.
>
> So it comes back to the question of what your material really is ...
>
> -Jason
>
>
> On Wed, Dec 3, 2014 at 2:39 PM, Jason Gaudet <jason.r.gaudet at gmail.com>
> wrote:
>
>> Hi Pushkar,
>>
>> Do you have a reliable source that tells you what Fe-O and Fe-S bond
>> distances and coordination your iron triflate should have?
>>
>> I'm not familiar with iron triflate but I was under the impression Fe was
>> coordinated to the sulfonate through an oxygen? And if so, even if your
>> sample didn't absorb water, you're trying to measure a S second-shell on
>> the other side of an octahedral O shell? And apparently you're correctly
>> fitting that O shell? Am I visualizing the structure correctly?
>>
>> If your concentration of Fe was very low, or your setup was otherwise
>> less than ideal (which, for catalyst studies, is pretty common), I would
>> not be surprised if your data quality isn't sufficient to distinguish S
>> scatterers on the other side of six O scatterers from your noise level.
>>
>> But without knowing the structure, or your sample setup, or your spectra,
>> all I can really do is imagine these things ...
>>
>> (And yes, it is hygroscopic.)
>>
>> -Jason
>>
>>
>> On Tue, Dec 2, 2014 at 8:22 PM, pushkar shejwalkar <
>> pshejwalkar2004 at gmail.com> wrote:
>>
>>> Dear All,
>>> I am experiencing problem during my fit for Fe(OTf)2
>>> anhydrous. The problem is as follows.
>>> I collected the data and used a model to fit. The fitting values and
>>> other technical information is as below. The basic problem is Fe(OTf)2 in
>>> anhydrous condition is probably not cyrstalline because of which there are
>>> no crystal data available. Although .cif file is available for hexahydrate
>>> and tetra acetonitrile. But obviously it is not directly useful as I am
>>> looking for Fe(OTf)2 only. I used hexahydrate for fitting, and the fit
>>> information is given. Is this fit acceptable?
>>>
>>> *Now two questions*
>>> 1) Why do I not see any scattering or peak for Fe-S. I expected S to be
>>> a strong scatterer and would show a peak. Under given circumstances it
>>> looks like Fe is all surrounded by water and no triflate is present near Fe
>>> at all. Is this assumption even make sense (when the bottle said anhydrous)
>>> The bottle was not kept under inert condition (and its my fault), but does
>>> it mean Fe(OTf)2 is so hygroscopic and that it can actually form such
>>> hexahydrate to the full extent?
>>> OR there is some inherent problem with my fitting and collection itself.
>>> I used RBKG=1.0
>>>
>>> 2) Is anybody working on Fe(OTf)2 and had such or any other problem
>>> indicating that Fe(OTf)2 by itself is a bad choice of precursor because of
>>> its reactivity. Also any comments on purification method etc. does anybody
>>> know if crystal structure is available for Fe(OTf)2 anhydrous? I could not
>>> find it on the quick search or on CCDC. Any other site where I can get
>>> crystal data and .cif information?
>>>
>>> Thank you very much for all the help, I hope the question is asked
>>> appropriately and all the other information is provided, however, if
>>> anybody needs any other information please let me know.
>>> Thank you in an anticipation
>>> Best
>>> Pushkar
>>>
>>>
>>> Independent points : 16.1250000
>>> Number of variables : 4
>>> Chi-square : 7324.9401796
>>> Reduced chi-square : 604.1187777
>>>
>>> R-factor : 0.0195782
>>>
>>> Measurement uncertainty (k) : 0.0001264
>>> Measurement uncertainty (R) : 0.0004142
>>> Number of data sets : 1
>>>
>>> guess parameters:
>>>
>>> SO = 1.06525455 # +/- 0.05504541 [1.00000]
>>> delE = -2.32587026 # +/- 0.59606221 [-2.77870]
>>> delR = 0.00911122 # +/- 0.00503027 [-0.02322]
>>> ss = 0.00706809 # +/- 0.00071967 [0.00300]
>>>
>>> Correlations between variables:
>>>
>>> delr & dele --> 0.9154
>>> ss & so --> 0.9023
>>> All other correlations below 0.4
>>>
>>> name N S02 sigma^2 e0 delr Reff R
>>> =========================================================================
>>> O1.1 6.000 1.065 0.00707 -2.326 0.00911 2.09150 2.10061
>>>
>>>
>>> --
>>> Best Regards,
>>> Pushkar Shejwalkar.
>>> Post-doctoral -Researcher,JSPS Fellow
>>> Hokkaido University,
>>> Sapporo,
>>> Japan
>>> [image: Inline image 3]
>>>
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>>> Ifeffit mailing list
>>> Ifeffit at millenia.cars.aps.anl.gov
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>>>
>>>
>>
>
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--
Best Regards,
Pushkar Shejwalkar.
Post-doctoral -Researcher,JSPS Fellow
Hokkaido University,
Sapporo,
Japan
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