[Ifeffit] Regarding a fit for Fe(OTf)2

[Jason Gaudet]

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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>
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