As per the controversy in 2013 in organometallic chemistry, my student is having problems also with the elemental analysis of square-planar platinum complexes. Not wanting to "make up" the results we thought it would be better to make a cogent argument about the difficulties with getting accurate EA for such complexes. Our analysis can only account for between 70 and 85% of the mass, otherwise the ratios are fairly ok (CHNPt) (within 0.5 to 1%). Does anyone know of any good references that detail the problems with elemental analysis of metal complexes, especially platinum? Our understanding is that additional non-volatile products for from the metal and the mass can "disappear."
If you can decompose your sample by heating and analyze the product by powder diffraction you may discover traces of platinum carbide/nitride that may lower the total amount of CO2/NOx analyzed by the elemental analysis instrument. Sometimes we obseverve similar behaviour for some vanadium complexes.
Hi,
Thanks. I will look into that. How do you get around EA then for publication in chemistry journals. I feel like there is this idea from the organic chemistry community that EA is full proof, but clearly it doesn't always work. We are two moths waylaid in publishing due to this issue as reviewers are intent to have it.
If you are sure about the composition of the sample and the EA is bad it is simply not a suitable method for the sample. I can suggest you to talk to a geologist who will surely recommend you a company dealing with elemental analysis of soil samples. They usually determine the amount of metals in the samples, but they can also determine C,N,O (elements with atomic number 5 and lower are not detectable by this method), moreover, they would determine Pt as well. It is more expensive then usuall EA but I believe it may solve your problem. One of the methods is called Wavelength-Dispersive X-Ray Spectroscopy (WDS) and you will need a crystalline sample. I guess google will tell you where this analysis can be performed :-)
For example, we have good experience with http://acmelab.com/ - but they use another method (I am not an expert in this field).
We have high resolution mass, readable H NMR (typically broadened by the platinum) but no C13 due to poor solubility. We have done Pt EA as well as CHN. WE know the composition of the samples. Solubility is our problem, but we have worked the synthesis to give what we believe to be clean samples and there is good literature precedent for similar compounds using similar synthetic methods. We have sublimed our ligands as well, so we know what is going into the reaction. I guess what I really want at this point is a good argument for ignoring the bad EA data. I cant find a good paper that details these problems. This is a general problem in science. No one publishes on how things fail, which is a shame.
Next week will will try to get a clean analytical HPLC trace in ethanol (sparsely soluble there). We are studying the photoluminescence and the trends of our series are interested and physical. A shame to dump the paper over one analytical method.
If you have any others I would appreciate it. Thanks for your help.
After a longer industrial activity, I was happy to see that nowadays many (some?) organometallic chemistry journals accept papers based solely on MS and multinuclear NMR without EA (or with EA only of your organic ligand). I had similar problems previously with EA as you with transition metal complexes, but seldom got a perfect fit for EA (just tried multiple analyses at different places until I got the values, which were close enough). So why don't you make an issue from it in a paper, which would perhaps convince even more 'negative' reviewers. I think you could try HMQC (or may be HSQC?) to get a 13C NMR (2D) spectrum from your diluted solution as this has much higher sensitivity than a simple 13 C NMR (you could also think of solid state NMR for Pt and C). Good luck!
First of all go for TGA from that get the complete decomposing temp. then at this temp burn your material for 30 min or more which will give you powder. then go for pXRD of your material and go for library search. most of the decomposed material are available in pxrd library. by that you can conclude what are the residue and why they are left behind. some times it may give you answers...
if you like my answer pls promote or demote... thank you
May be the determination of Pt discribed in [ Russian Journal of Coordination Chemistry, 2007, Vol. 33, No. 2, pp. 111–115. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © O.V. Dolotova, O.L. Kaliya, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 2, pp. 116–120.] will usefull for you.
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