The Cobalt Hydride that Never Was #chempaper 216

In 1971 a Co-H complex was reported by Schrauzer and Holland. The chemical shift of the hydride was suspicious for this complex. So, finally the correct structure of the complex and the assigned proton NMR are reported here in addition to the paramagnetic species. Really good work.



http://pubs.acs.org/doi/abs/10.1021/jacs.5b01838

Third row transition metals for the treatment of cancer #chempaper 215

Among the metal based anticancer complexes, third row metal-based ones are the most common. In fact, Pt-based ones like cisplatin, carboplatin, oxaliplatin are really effective anticancer drugs. In this article, the authors summarize the mechanism of "classical" Pt-based anticancer complexes and briefly talk about the new "monofunctional" complexes (pyriplatin, phenanthriplatin). These are Pt complexes with a net + charge and they are trying to exploit the organic cation transporters. Finally, there are a few examples of really active Os(VI) based complexes.

http://rsta.royalsocietypublishing.org/content/373/2037/20140185

Targeted delivery of platinum-based anticancer complexes #chempaper 214

Platinum based anticancer drugs are widely used in several types of cancers. One of the problems using these drugs is the toxicity and efficient delivery of the complexes. People have been studying different drug delivery methods and this article summarizes tens of them.

http://www.sciencedirect.com/science/article/pii/S1367593113000057

Approaches to the design of catalytic metallodrugs #chempaper 213

Well, we can do catalysis using transition metals. Can we do the same in biological systems? Moreover, can we do biochemical transformations? The answer is yes, we can and here are a few examples of these remarkable processes.

In this brief review, you can read several examples of metal catalyzed cross coupling reactions for fluorescent labelling, deprotection of azides/carbamates, activation of metallodrugs, cleavage of peptides, nucleic acid chains and proteins (HIV1, RNA etc.), using NADH for transfer hydrogenation and many more transformations that are done in biochemical environment. Some of them are their infancy, but there are some in Phase II/III stages and there is even one approved in Russia.

Is there a common chemical model for life in the universe? #chempaper 212

Fantastic article on what life is and whether we can find it elsewhere. Biology and life itself drives me crazy and I want to see the discovery of other or similar life forms before I die. The authors ask all the questions you could possibly ask. If you are one of those who ask "Why?" a lot, this article is definitely for you.

http://www.sciencedirect.com/science/article/pii/S1367593104001358

Why 20 amino acids?
Why 4 DNA bases?
Why carbon?
Why water?
Could any other solvent support life?
and tens of other questions are really well explained here. The references are so great that I will probably end up reading 50 of them.

Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel(IV) complexes #chempaper 211

This is the second octahedral organometallic nickel (IV) complex and also shows a unique reactivity. These made it into Science I guess. When I say I am not much impressed by the paper, people tell me that I am absolutely wrong. But, I still think the same. It's cool, what it does is very cool, I respect the way to make it and isolate it, but I think there will be many more interesting Ni(IV) compounds and unfortunately I think many of them won't be able to make it to Science.

http://www.sciencemag.org/content/suppl/2015/02/04/science.aaa4526.DC1.html

Rhodium-Catalyzed Hydrosilylation of Ketones: Catalyst Development and Mechanistic Insights #chempaperaday 210

It's a very nice review on hydrosilylation with rhodium catalysts. Not the most recent, but a very good one.

There are very active and selective Rh catalysts out there, but the price of rhodium makes it less attractive. So, there is huge effort on developing catalysts with cheaper first row transition metals. Nevertheless, mechanisms of Rh catalyzed reactions are pretty well understood for now and it's still an active research area.

http://pubs.acs.org/doi/abs/10.1021/cs200571v

Book: The Kaiser's Chemists: Science and Modernization in Imperial Germany

This book is a great source on the history of chemistry and its relation with politics, governments and of course war. 

By the end of the 19th century, some German chemists (Emil Fischer -"a pillar of militarized science" in particular) started to think that they were losing their position in chemistry (especially in inorganic chemistry) to the US. "We must do more for inorganic and general chemistry again, if we are not to be put to shame by other countries."

 

Fischer and several other chemists decided to convince the Kaiser to fund chemistry and open new labs. What they had in mind was a large research facility with the most modern equipment. So, it took years and a lot of PR to convince companies and the Kaiser himself to open these research centers. Not surprisingly for those years, about half of the funding came from Jewish businessmen (you can read the reasons in the book). These centers, in turn, brought much success to Germany and tens of Nobel Prize winners. 

 http://en.wikipedia.org/wiki/Wilhelm_II,_German_Emperor

The best part of the book in my opinion is that it allows you read the discussions among academicians and politicians regarding the importance of funding, research ideas and commercial applications of the products. Just like today, many chemists believed that chemistry was no longer a career or how little chemists were respected. There were also fights among several professors on why there were few positions (or too many chemists). On the other hand, there were chemists telling that there were too many professors at upper ranks. Professors complaining about teaching duties... Basically, everything was exactly the same as today.

There are also so many details that I didn't know about such as the rivalry between Nernst and Haber, Willstatter's research interest in photosynthesis in the living leaf, Einstein's pacifist letter with only 4 signatures and Fischer's wish for Haber's tests "failure from the bottom of my patriotic heart"

Some interesting quotes:

"Science did not escape the rise of nationalism but adapted to it.

[Ostwald] it was not frequently claimed that I was no chemist, because I never produced a new substance.

Big science, like big industry, needs operating capital.

Standstill is retreat (Duisberg).

As an Austrian women, a Jew and a physicist, Meitner's presence meant little to the German chemists....with the nonposition of unsalaried "guest".

[A university professor] is freer, because he can replace many assistants by students and doctoral candidates.

[Harnack] our enemies...brought German science and military strength as close together as possible.

[Liebknecht] science and research in uniform have hardly ever done good.

...the war converted him [Ostwald] virtually overnight, to an ultranationalist. "

Pauling's Left-Handed alpha-Helix #chempaperaday 209

Left-handed alpha-helices are not common. In fact, I was able to find only one example with my limited search attempts although I am sure there are many more. There are stereochemical issues, bond distance and dihedral angle restrictions if nature or  you want to make one of them. So, when I first saw the title, I did not want to believe that Pauling proposed a left-handed alpha-helix. I thought he just made a mistake in one of his books or papers. If you read the paper, you will see that this is not the case. For some reason unknown to us, he drew this helix. As the paper explains, in fact he made an arbitrary assignment to R groups when he first reported "the structure of proteins."

 http://www.pnas.org/content/37/4/205.full.pdf

But, as the author explains in detail, he should have known the absolute configuration of the amino acids. In fact, his colleagues at his own department were doing research on the subject. So, he should definitely have known much more about his "incorrect" assignment. You can read the article and learn more about the issue. My own understanding is that he was not in close communication with his faculty members in those years due to the political troubles he had had. Maybe the people who really knew the absolute configuration did not correct him on purpose, or he did not want to be corrected by one of those people who were not on his side when he needed support. But, I don't think he was simply not "interested in the problem of absolute configuration." I think this is contrary what we know about his scientific curiosity and genius.

The author is Jack D. Dunitz who is a giant in his field and you may know his name if you can remember Burgi-Dunitz angle.

Elongated dihydrogen complexes: what remains of the H–H Bond? #chempaperaday 208

Most transition metal dihydrogen complexes have an H-H distance less than 1 Angstrom. The rest of the complexes have longer H-H bond distances making them what is called "elongated dihydrogen" complexes. Of course if the distance is larger than 1.5 they become dihydride compounds.

http://pubs.rsc.org/en/content/articlelanding/2004/cs/b304879a#!divAbstract

In this short review, there is a lot and much useful information for those who want to learn more about these interesting complexes. Because it is difficult to resolve the crystal structures containing these ligands, there are a few methods to characterize them. Probably the simplest method is to use HD and measure the coupling constant and then plug it in in this formula :

There are ten "representative" complexes in the article that really help you to get a better understanding. I like the idea of listing these complexes and giving details about them. I think more authors should try this type of writing. Most review articles only cite other papers and avoid giving detailed information which makes following the paper really hard in some cases.

At Least 60 Years of Ferrocene: The Discovery and Rediscovery of the Sandwich Complexes #chempaperaday 207

This is probably one of the most interesting and surprising articles I have read. 

I guess all inorganic/organometallic chemists know (I hope) the story of the discovery of ferrocene and other sandwich complexes. It all starts with Pauson and Kealy's Nature papers on the discovery of an unusually stable compound ("What was this remarkable substance we had made?") and goes on. I will not go into the story. If you want to learn, you should read this paper and many other historical papers on these compounds. Later, it turns out that in fact they were not the first people to discover this compound. Many other people had already seen this complex but they simply did not report it. The compound gets attention from several chemists including Woodward, Fischer and Wilkinson. In fact, the name ferrocene was given by Woodward. Soon, the competition between Fischer and Wilkinson started. They literally divided "the periodic table between them".

This is an incredibly well written story. The most interesting two things for me are the comments of a reviewer and Woodward's comments on the Nobel Prize in Chemistry.

First, the referee writes to Woodward "We have dispatched your communication to the printer but I cannot help feeling that you have been at the hashish again."

Secondly, Woodwards writes to the committee on the Nobel prize saying "...I am sure-committed a grave injustice...Both of these concepts were simply, completely, and entirely mine, and mine alone." wow!

"Modeling the Active Site of [NiFe] Hydrogenases..." #chempaperaday 206

I found this paper very good both in the quality of research and explaining simple but important details about hydrogenases. Contrary what many people think there is not one type of hydrogenase. There is a recent and very good review here if you are interested. I will read it soon,

http://pubs.acs.org/doi/abs/10.1021/ic500910z

Michele Peyrone, Discoverer of Cisplatin #chempaperaday 205

Cisplatin is a very effective anticancer drug especially against testicular cancer. It is also probably one of the most important metal complexes that opened a new research area for developing anticancer drugs. Its biological activity was discovered accidentally by Barnett Rosenberg and colleagues and it was approved by FDA in a very short time compared to any other drugs. 

Anytime you read a biochemistry or bioinorganic chemistry paper about metal anticancer complexes (covalent ones especially), you can read a very similar introduction. But, some of them also mention that the complex was synthesized almost 100 years prior to its "fame". Cisplatin was first synthesized by Michele Peyrone in 1844. Knowing nothing about isomerism of course, Peyrone described the physical properties of the compound and hypothesized its forming. It was then named as Peyrone's  Chloride.  I found it very interesting that Peyrone worked under Justus von Liebig. Later, Peyrone focused on agricultural chemistry and did not pursue his studies on platinum compounds.

The article is written by four authors and the name George B. Kauffman caught my attention of course. I know his writings very well and try to read as many as possible. 

It was good to know Michele Peyrone closer and I suggest you do the same.

Book: "Linus Pauling and the Chemistry of Life"

I said it before and I will say it again. Linus Pauling deserved to win 3 unshared Nobel Prices in chemistry. In any field of chemistry, you can see his impact. He's always there.

This book is probably the best biography of Linus Pauling. I opened the book a very late time at night and I just couldn't stop reading it until I finished and I wish it had not finished. Such an amazing storytelling. I knew a lot about his life even before reading the book, but I still learned a lot. I knew he had trouble with government but I did not know that FBI investigated him for 24 years and some of the funding agencies cut his research funding. He had really hard time finding a place to work! What a shame. How unfair! 

There is no other chemist that revolutionized chemistry and medicine as much as he did. He was a true genius and it's a shame that for decades he was alienated by his colleagues and his government.

Book: "The Devil's Doctor"

Since I discovered Philip Ball and his writings, I have been reading everything he produces. In my opinion, he is by far the best science writer. I am also interested in reading everything about Paracelsus since I consider himself one of my heroes in science and medicine no matter what people think about him. I think he played a very important role in modernization of chemistry and medicine. 

If you think this book is an ordinary biography, you are mistaken. The book is really well written with the most interesting stories and endless journeys of Paracelsus. You will not only read his life, his work and trips; but also the political and religious environment of his age. 

If you ever read anything about Paracelsus, you probably know that he traveled almost anywhere accessible in 16th century to learn how different people fight the diseases. He was outspoken, and he had "extreme" ideas and sometimes practices that gave him trouble. To him, schools were not really the only places that you can learn a profession: "At all the German schools, you cannot learn as much as the Frankfurt fair." Traveling was so important for him that once he said "If a man wishes to recognize many diseases, let him travel." 

I think the book is a fascinating work on Paracelsus. Unlike several other books, the book does not have a fixed idea on Paracelsus' character or whether we should take him seriously or not. This makes the book even more special by allowing us to have our own opinion.

I strongly recommend this book for science, medicine, philosophy, philosophy of science and chemistry enthusiasts. My personal opinion is that Paracelsus was a great man and scientist and we owe him a lot. Since I first heard of his name when I was a little boy, I always felt very close to him. What I like him the most as Philip Ball says "always he was no one's man but his own."

Colors!

A friend was making some starting materials and [they] allowed me to take some photos of these beautiful compounds. Bright colors are definitely among the top reasons to love inorganic chemistry.

Technetium Chemistry in the Fuel Cycle: Combining Basic and Applied Studies #chempaperaday 204

Technetium is the most mysterious element. In the middle of the d-block and yet radioactive. You can't just dig and find technetium (therefore the name). Despite all these difficulties, the isotope ^99mTc is the "workhorse of diagnostic nuclear medicine." It is the byproduct of fission reactions of uranium isotopes in the reactors. Because, it requires special handling and other requirements, not every lab is lucky to study technetium chemistry. So, not much is known about it yet. All I know is that it makes nice bimetallic complexes with multiple Tc-Tc bonds. So, I was not much surprised to learn that "[on binary compounds]...only three species, TcF₆, TcF₅, and TcCl₄, identified prior to 2008."

A few more details from the paper:

Because of its high fission production rate, the amount of technetium on Earth may ultimately exceed that of rhenium, its heavier congener.  

In a typical light water nuclear reactor, ⁹⁹Tc production is around 2 g/day for every 100 MW of thermal energy. 

Technetium has a range of oxidation states, from 7+ to 1–, and its chemistry has considerable similarities to rhenium; e.g., it has extensive pentavalent chemistry. 

The overall trends clearly demonstrate increasing technetium–technetium interactions with decreasing oxidation state.

A Half-Century of Nonclassical Organometallic Chemistry: A Personal Perspective #chempaperaday 203

The 100th #chempaperaday was "A millennial overview of transition metal chemistry" by F.A. Cotton. Interestingly enough, my 203rd paper is another great article by him. 

http://pubs.acs.org/doi/abs/10.1021/ic010972n

In this article, he highlights a few selected areas of inorganic chemistry and obviously his contributions to these areas. In fact, he paved the way for several of these. When chemists just put their hands on an NMR instrument, he started to do VT experiments to study the fluctional behavior of several organometallic compounds. Incredible work. There is also a few pages on the iron dimer that I just posted, the discovery of agostic interactions, his proposal to use hapticity and so on.

"Prior to the report on ferrocene, no one worked in the field of transition metal organometallic chemistry because no one believed that there was any such field to work in."

Does cyclopentadienyl iron dicarbonyl dimer have a metal–metal bond? Who’s asking? #chempaperaday 202

A really nice article on why we should draw  a bond between iron atoms in this complex. I presented this paper later to a group of people. I defended Jay Labinger's view and my own literature search and the evidence (homolytic cleaveage to give 17 electron radical species etc.) I saw made me think that we should draw a bond. If you like controversies and discussions on transition metal complexes like me, you will enjoy it.

I should note that the article has quotes from Galileo, poems from Dante and Pushkin. It is not very often you see these types of things in articles which made me like the article even more.

http://www.sciencedirect.com/science/article/pii/S0020169314002278

A few quotes:

 ..given Al Cotton’s intimate involvement with the history of both M–M bonds in general and Fp₂ in particular – not to mention his fondness for engaging in polemics.

The latter argues against E. O. Fischer’s description: probably this constitutes Cotton’s first polemic in print!)

The metathesis reactions: from a historical perspective to recent developments #chempaperaday 201

A nice historical perspective of olefin metathesis and metathesis catalysts. The article was published in 2005. So, don't expect to see exciting new stuff like enantioselective ones.

I remember writing on metathesis before. So, let's add some new things that I learned.

"..the first observation of the metathesis of propene at high temperature was reported in 1931.

Schrock, then at Du Pont, tried to synthesize [Ta(CH2CMe3)5], which would not contain b-hydrogens and thus, according to this principle, should have been stable. Good luck smiles only on good scientists, and the expected compound did not form...led to the isolation of the first stable metal-alkylidene complex, [Ta(CH2CMe3)3(=CHCMe3)]."

"Exploration of Earth-Abundant Transition Metals (Fe, Co, and Ni) as Catalysts in Unreactive Chemical Bond Activations" #chempaperaday 200

This is a short article on Fe, Co and Ni catalysts towards C-O, C-C and C-H activation. My purpose to read this article was to see "what is out there" and see if I can learn a few new things. I want to point out a few important (at least for me) details in this article on the characteristic behaviors of these metals. As an inorganic chemist, I enjoyed these parts the most.

Fe : Let's repeat that it is the most abundant transition metal on earth.

Co : Like iron, it is cheap and abundant. But, in these type of bond activation reactions, Co catalysis "lagged greatly."

Ni : $1/g ! Unbelievable! The congeners of Ni; Pd($183/g), Pt($483/g)! Oxidative addition of Ni(0) or Ni(I) usually goes through SET processes. And as we can see from the beautiful periodic table, Ni is more nucleophilic as expected. The authors also claim that Ni is "the best metal to induce the C-O cleaveage of various O-based nucleophiles."

There are lots of examples of bond activations and catalytic cycles in the paper. I noticed an error in one of the figures:

Also, one of the authors was born in 1991 and he is a ""third year graduate student." 

"A Nickel(II)–Sulfur-Based Radical-Ligand Complex as a Functional Model of Hydrogenase" and the "controversy" #chempaperaday 197-199

The first paper came out in 2010 and reported synthesis and characterization of a Ni(II)-dithiolene complex. The authors formulated the compound as Ni^II(L²⁻)(L^−.)][PPh₄] and claim that complex "shows strikingly similar EPR and reduction potential values to those observed with native Ni-containing hydrogenases." I should mention that CV of the compound was reported in MeCN. You can read the paper and ask questions, but the most interesting thing they did not provide a proton NMR spectrum for this paramagnetic compound. But, they assigned a signal at 4.1 ppm to a S-H. Interesting.

Anyway, shortly after a "comment" was published  and proposed a new oxidation state assignment for the Ni atom and the ligand. A "Response" followed and honestly I don't think they added any new evidence or supporting argument for their own assignment.

I still think, they are worth reading.

Book: The Violinist's Thumb

I got this book as a gift. As I read The Disappearing Spoon by the same author before, I was expecting it would be as entertaining and interesting as it was. I think this is a good book to read, but if you already know some about biology, genetics, genes and some evolution; I don't think you will learn much. I read it quickly and I liked it (3 stars). There are several interesting stories, but in my case, I knew most of them. Anyway, I still think it is worth reading since there are a lot of names and details. Also, you will have a lot to learn if you do not know much about science.

http://www.amazon.com/The-Violinists-Thumb-Written-Genetic/dp/0316182311

A Salute to My Colleague Yves Chauvin, 1930–2015 #chempaperaday 196

Olefin metathesis is one of the most important and useful chemical transformations. The earliest versions of this reaction involved using not well defined catalysts and the reaction mechanism was not understood. In 1971, Chauvin proposed a mechanism that is accepted as the actual mechanism of the reaction today.

metathesis mechanism (source:wikipedia)

Chauvin died on January 27. I have read about him before. But, I think this is the best article.
Here are a few quotes from him proving how good a scientist he was:

“If you want to find something new, look for something new!”

“Some people say that there is too much chemistry in our society. It is in fact the opposite: there is not enough chemistry, not enough understanding, not enough control of chemical reactions. Catalysis is the key for a better chemistry.”

Visible-Light-Driven CO2 Reduction with Carbon Nitride: Enhancing the Activity of Ruthenium Catalysts #chempaperaday 195

A carbon nitride and ruthenium complex system with 4 different Ru complexes are reported in this article. The authors state that these results are "the best values that have been reported for heterogeneous photocatalysts for CO₂ reduction under visible-light irradiation to date." I am trying to design and synthesize homogeneous catalysts, but I always have great interest in heterogeneous systems.

 

Below you can see their CO2 reduction abilities.