Hydrolytic cleavage of both CS2 carbon–sulfur bonds by multinuclear Pd(II) complexes #chempaperaday 284

C-S activation is as important as C-O activation. There are sulfur containing compounds (impurities) in petroleum products and separating them from the desired product is not as easy as it may seem. These sulfur containing products can "poison" catalysts and also have some not so desired affects on the environment. Although not as common as CO2 activation, you occasionally see some CS2 activation. But, cleaving both C-S bonds in CS2 has not been seen. Well, until now. Here the authors use a Pd complex that also exists as a dimer in solution to cleave these bonds. Moreover, they were able to convert CS2 into CO2 and SO2 through really cool mechanisms (proposed). VERY COOL chemistry.

http://www.nature.com/nchem/journal/v9/n2/pdf/nchem.2637.pdf

Why copper is preferred over iron for oxygen activation and reduction in haem-copper oxidases #chempaperaday 283

I wish I had more time tonight at least write a little bit about haem–copper oxidases, but it is late and I have other things to do. I may write about them as a separate post later. 

I know a little bit about the preference that is mention in the title, and read some papers trying to explain the choice of copper (I remember a PNAS paper for example). Anyway, I think this paper finally explains the nature's choice without any doubt. Here they modified a haem–copper oxidase in myoglobin and were able to fully characterize a Cu, Fe and Zn bound haem–copper oxidase. The detailed studies show that copper is superior owing to its more electron rich character and higher reduction potential (activates O2 better). A fantastic paper by Yi Lu.

 

http://www.nature.com/nchem/journal/v9/n3/pdf/nchem.2643.pdf

Identification of the Formal +2 Oxidation State of Plutonium #chempaperaday 282

Here is another plutonium paper this month. Looks like March is (was) the plutonium month. I will copy and paste from the abstract so that I don't say anything wrong about the impact of the paper:

"the first structural characterization of a Pu–C bond. Absorption spectroscopy and DFT calculations indicate that the Pu²⁺ ion has predominantly a 5f⁶ electron configuration with some 6d mixing."

I really appreciate the team's effort to try to fully characterize the compounds here. Think about it, there is some real radioactivity concern first of all. Secondly, since the plutonium is weapons-grade, I am pretty sure there is a lot of concern about material being lost/wasted etc. Nevertheless, they managed to collect the characterization data that is necessary. In addition to the data, they also provided some photos of the compounds and the crystals which I think are really cool. You don't see plutonium compounds often. What I really liked though is the explanation (which I totally agree) they provided for the solvent impurities in the NMR samples. From the SI:

"Solvent  impurities  in  the  deuterated  solvents  in  this  spectrum  and others  are  difficult  to  eliminate  because a negative pressure glovebox , operated for safe containment of transuranic  α - particle emitting radioisotopes , cannot have the  atmosphere purged for safety reasons (pressure  inside  the  box  must  remain  negative  relative  to  the  laboratory  atmosphere at  all  times ). Once  discovered  by  NMR , it  would  take several weeks  of  work to  repeat  the plutonium experiments  and attempt to remove all traces of solvent  impurities (which may not be successful) . Since these  impurities  do  not  change  the  results  or  conclusions ,  the  aesthetic  improvement  that  might  be  gained from the extensive work required was not pursued."

Overall, great work I think!



http://pubs.acs.org/doi/pdf/10.1021/jacs.7b00706

Most downloaded ≠ Most read

Yesterday at ACS San Francisco conference, a paper (and its first author) was awarded for being the "most read" in 2016 by Organic Letters. Apparently, the metric that was used was "most downloaded" article. I have some objections against it. If an article has been downloaded X times, does it really mean that it was read X times? I don't think so. Moreover, what is the source of the downloads of the article? If a professor assigned the article to his class and they all downloaded it, does it really mean that the article was "read"? Maybe it was assigned for an NMR lecture? Since I don't know the details, the metric that was used may have been "most viewed" too. According to the webpage, it was viewed 90,594 times as of now. But "most viewed" is even less reliable than the "most downloaded". Just post the link on Reddit and a few other news outlets and if you get enough attraction, you get 100K views in a day.

According to Web of Science, the article has been cited 0 times (or 1 according to here, or 3 according to Google Scholar) so far. This is not really surprising since it came out only in 2016. But, there are articles that are not "read" as much as this one and they are cited 10+ times already. In the end, I have my own problems with citations anyway. I think being cited also does not mean being read.

I wrote it before, I am against using metrics such as "most read", "most downloaded" and "most viewed" since they tell absolutely NOTHING important to anyone. And they may become new impact factors for the young people who rely on internet more than anything else.

Note: I have no relationship with any of the authors or the research area of the paper. I also congratulate them for their research and publication. I read it in the science news last year and I understand the importance of the discovery.

http://pubs.acs.org/doi/abs/10.1021/acs.orglett.6b00979

A Structurally Characterized Organometallic Plutonium(IV) Complex #chempaperaday 281

Here is the synthesis and crystal structure of Pu(1,3-COT’’)(1,4-COT’’)(4;COT’’ = h

8-bis(trimethylsilyl)cycloocta-tetraenyl). At first I was trying to understand why they decided to prepare this sandwich complex with two different ligands. Later I realized that there is a silyl shift during the oxidation reaction! The authors discuss the reason and suggest that the shift may be due to some hyperconjugation/stabilizing effect (read the DFT part) I have isolated some weird things from my reactions several times. You never now what really happens until after you isolate these kind of interesting products. It is very common that Early metals, lanthanides and actinides give you really unexpected products. Another interesting note: like the other lanthanides, they again use CoCl2 as a oxidant! 

 

 

 

http://onlinelibrary.wiley.com/doi/10.1002/anie.201701858/epdf