#chempaperaday Day 32/365: "New insights into the chemical and isotopic composition of human-body biominerals. I: Cholesterol gallstones from England and Greece"

I had to give up my #chempaperaday challenge for a few months. As some of you might know, I applied to graduate schools and got some answers. So, I spent some serious amount of time THINKING about my future. I just couldn't concentrate on anything else. I couldn't concentrate on my classes, my personal life, friends etc. After I made my final decision, I started to prepare myself towards what I am going to do in grad school (Yes, I know where I am going to and what I am going to do there.). So, I read TOO MANY inorganic chemistry papers and books. Once again, I started to feel relaxed. That's why, it's time to go back to reading and writing.

I can safely say that I am starting my Ph.D. in a few weeks. But, I will still wait to announce it here until I get the paperwork in my hands. 

I decided to start my posts with a paper I read a few weeks ago. The researchers (mostly from Greece) studied 20 gallstones from four patients and finally chose four gallstones to use for their research purposes. Using several different analytical and spectroscopic techniques, they conclude that calcium is the most abundant metal in gallstones. I was surprised to see there is also some Sr in the samples. But, it can be explained by the similar ionic radius of Sr to Ca. 

image: http://users.uoa.gr/~agodel/Pics/Gallstone.jpg

Interestingly, Zn and Mn was only found in the samples from England and they were rich in Pb, As and Ni. The authors note this fact as follows:

"Thus, gallstones from England are mostly rich in toxic elements."

"A Case History: The Determination of the Solid-state Structure of Triiron Dodecacarbonyl"

I tried so hard to come up with a title for this post. But, I really think there is nothing more interesting than the title above. I will write a very brief summary for the history of the compound and give some great links to read more about this fascinating story.

I built this one using Avogadro. 

image: wikipedia

Triiron Dodecacarbonyl was first synthesized by Sir James Dewar (Yes! the inventor of the Dewar flask) in 1907 and it was the third iron carbonyl complex that was discovered[1]. But, it took about 20 years for chemists to determine the molecular formula. In the next ~ 10 years, several structures were suggested by different chemists. The speculations and discussions continued and by 1963, there was enough evidence suggesting that three iron atoms were located in a triangular geometry, and two of them were equivalent (can be seen in Mossbauer spectrum below). 

In 1965,  a series of interesting events led Nils Erickson to determine the correct structure. 

He was a graduate student who was studying Mossbauer spectra of some iron complexes. But, it looks like it was not easy for him to publish his findings:

Finally in 1974, Cotton published a "further refinement" for the structure. I think this story clearly shows how important Mossbauer Spectroscopy is. I don't know when, but the first time I will look at a Mossbauer spectrum, I will definitely remember this great story.

Below you can find all the papers I have read about this complex and the events and research that led to the determination of the structure. 

1. The Tortuous Trail Toward the Truth 

A Case History: The Determination of the Solid-state Structure of Triiron Dodecacarbonyl

2.  Further refinement of the molecular structure of triiron dodecacarbonyl 

3. Mossbauer Effect in Iron Pentacarbonyl and Related Carbonyls

4. Mossbauer Spectra of Iron in Na,[Fe(CO),] and Na [Fes(CO)llH1 and Comments Regarding the Structure of Fe3(CO)

Book: NMR, NQR, EPR and Mössbauer Spectroscopy in Inorganic Chemistry

When I read a book and if like it, I try to buy it. I really love this book, but even the used ones start from $88 on Amazon. So, it looks like I will not be able to own this book for some time. But, I tried to write down as much as possible for my notes until I buy one.

So, the book is about four different methods as you can understand from the title. As the author says in the preface, the book "is not a spectroscopic textbook, nor is it written for those with a need for detailed theory."  There is really very little about the theory of the techniques and they were kept as simple as possible. I was able to understand almost everything without any further reading or help. 

To be honest, I don't remember seeing any NQR spectra in publications and that's the only chapter I didn't pay much attention. 

What I like the most about the book is the chapter problems which are mostly from  journal articles. So, you are given a spectrum and asked to interpret it. Or you are given the complex and asked to make an educated guess on how the spectrum should look like. Or calculate isomer shifts, g values etc.

I wrote a post about one of these simple problems here. After studying the chapter on NMR, I dived into some papers and tried to apply what I learned. I am happy that I was able understand them better. 

I have also just finished two Mossbauer spectra posts and right now I am trying to read some literature so that I can write a longer and more detailed discussion for my posts. I also discovered a fascinating story on the determination of a molecular geometry for a transition metal complex. It is really amazing and I loved it. I will write a summary of the story and link all the published data and discussions in a post hopefully this weekend. 

In summary, I think this book is a must read/study book for a student like me. If I were teaching inorganic chemistry and spectroscopy, I would also ask similar problems in my exams.

NMR problems about transition metal hydrides

I have just done some NMR practice and I thought I should write about them.

So, the problem asks to assign four different Pt and Pd complexes to each spectrum given. (only high field is given)

Here are the spectra and the complexes ( I will explain the reasons below the figure):

1st complex and its spectrum: There is a bidentate ligand so the complex has to have cis geometry. This makes two phosphines non-equivalent and the complex should give two sets of doublets (doublet of doublets). 

2nd complex and its spectrum: So, there are two doublets of triplets. Triplets are due to the cis phosphines and the doublet is the result of the trans phosphine. The weaker resonances on each side of the spectrum are called satellites and maybe I should write a paragraph about them in a future post. (Only Pt-195 isotope has a spin and its abundance is 33%.) 

3rd complex and its spectrum: There are two equivalent phosphines (trans). So, this complex should just give a triplet. No satellites, because the metal is Pd.

4th complex and its spectrum:  There are two equivalent phosphines and we expect to see a triplet. We can see the satellites again due to Pt metal center.

 

A simple enthalpy and heat problem

I was reviewing physical chemistry and I saw a problem where you are supposed to calculate the heat required to produce Mg2+(g) starting with 1.00 g Mg(s) at 25 C.

This is a simple problem and here is the solution.

The interesting part (for me) is that to learn this heat is almost same as the heat needed to vaporize 43 g of water. It's ~ 97.24 kJ.

Metals and the Brain I

I have read several papers and books on metal ions in neurodegenerative diseases. So, I decided to start another series of posts as long as I find something to write on the topic.

I just read this article in one of my favorite magazines; The Scientist. I think it is a great review on copper in Alzheimer's disease. I read some of the references long time ago and I think I will read them all as soon as possible. Because, I do not know anything about pharmacology, kinetics of drugs etc., I usually try to understand the structures and read the papers very fast. I do know how to interpret IC50, Ki or other very basic data, graphs or values though. While at it, I should mention that there is a free online medicinal chemistry course on edx.org and it is in the 3rd week I guess.

Although we still know little about the true roles and concentrations of the metal ions, new and more powerful techniques (like X-ray fluorescence as the article mentions)  help the scientists to have better information each day. 

Several transition metals are essential for biological processes. One of the most important ones for brain is copper. Actually, the highest concentration of copper in body, is found in brain [1]. So, it is not surprising to see it as a key in neurodegenerative diseases such as Prion diseases, Wilson's disease and Alzheimer's disease. Recently, a group of scientists suggested that zinc is not a biomarker for Alzheimer's Disease. But, as Nigel Hooper says "these data do not rule out a role for altered zinc in the brain being involved in the disease process." Some of the authors of the research article are also working in the same university with the The Scientist article writer. The writer also mentions something similar :

Although overall zinc and iron levels did not vary significantly between AD and healthy brains in Kirsch’s 2011 meta-analysis, this doesn’t rule out complex subcellular changes to the location of these metals.

Even though one can determine the malfunction of the regulation of the metal, the biggest challenge is to fix the problem. One of the methods is using metal complexes (chelates). Here is a library of them by the same author's publication:

In summary, there is a lot of way to find out the cause and the cure for these diseases and I think this is a great article with beautiful infographics and I strongly suggest reading it.

http://pubs.rsc.org/en/content/articlelanding/2010/mt/c0mt00006j#!divAbstract

1. Hughes, M.N.; The Inorganic Chemistry of Biological Processes ; Wiley and Sons, 1981;  p 298.

42nd Annual James R. Killian Jr. Faculty Achievement Award Lecture:Understanding and Improving Platinum Anticancer Drugs

If you have been following the blog for some time (or if you actually know me), you must know that I am also interested in metal based anticancer drugs. Today I attended Stephen Lippard's award lecture at MIT where he gave a talk about platinum anticancer drugs for 1.5 hours.

Here is the recognition for his work and award:

Stephen J. Lippard, who is widely acknowledged as one of the founders of the field of bioinorganic chemistry, is this year's recipient of MIT's James R. Killian Jr. Faculty Achievement Award.
Established in 1971 to honor MIT's 10th president, the Killian Award recognizes extraordinary professional achievements by an MIT faculty member.

In announcing this year's award at the May 15 faculty meeting, the award committee noted that Lippard's groundbreaking work has pushed back the frontiers of inorganic chemistry, while simultaneously paving the way for improvements in human health and the conquering of disease.

Lippard, the Arthur Amos Noyes Professor of Chemistry, has spent his career studying the role of inorganic molecules, especially metal ions and their complexes, in critical processes of biological systems. He has made pioneering contributions in understanding the mechanism of the cancer drug cisplatin and in designing new variants to combat drug resistance and side effects.

His research achievements include the preparation of synthetic models for metalloproteins; structural and mechanistic studies of iron-containing bacterial monooxygenases including soluble methane monooxygenase; and the invention of probes to elucidate the roles of mobile zinc and nitric oxide in biological signaling and disease. 

 Especially, he focused on one of his recent projects : Osmium complexes. I also think that he is equally interested in Pt(IV) complexes. It was great to see and listen to him again after ACS Dallas national meeting.

My ACS Dallas experience

Since this blog is also my diary, I thought it would be a good idea to write down the talks I have been to at ACS Dallas this year. 

First of all, it was the greatest experience I have had as an undergrad. I have seen so many great chemists and I had the chance to listen to some of them. Unfortunately, we left the meeting on Tuesday at noon, so, I missed many great talks. 

X-ray fluorescence imaging and metalloproteomics: Tying images of metals in cells to the proteins that bind them
Lydia Finney

Metal-halogen secondary bonding in iron(II), cobalt(II), and nickel(II) 2,6-dihalophenolate complexes: Insights into the substrate specificity of the hydroquinone dioxygenase PcpA
Timothy E Machonkin, Monica Boshart, Jeremy Schofield, Patrick L Holland, Dalia Rokhsana.

Phosphoryl transfer enzymes: Theoretical studies of native enzymes and ground-state and transition-state analogs
Charles Edwin Webster, Katherine N. Leigh, Roger G. Letterman, Nathan J. DeYonker.

Reversible pyranopterin cyclization in synthetic models of the molybdenum cofactor
Benjamin R. Williams, Sharon J. N. Burgmayer, Anna Kalinsky, Yichun Fu.

Nitric oxide reactivity of the site-differentiated cluster [Fe₄S₄(LS₃)L']²⁻
Eric Victor, Stephen J Lippard.

Bimetallic complexes of rhodium dibenzotetramethylaza[14]annulene ((tmtaa)Rh): Structure, reactivity, and thermodynamic studies
Bradford B Wayland, Gregory H Imler.

Synthetic analogs for reduced [2Fe-2S] cofactors and for Rieske centers Franc Meyer, Antonia Albers, Serhiy Demeshko, Sebastian Dechert, Eckhard Bill. Bioinorganic meets organometallic: A tetracarbene-oxoiron(IV) complex Franc Meyer, Steffen Meyer, Iris Klawitter, Serhiy Demeshko, Eckhard Bill, Oliver Krahe, Frank Neese Controlling catalytic processes through ligand design Robert H. Grubbs Catalytic additions of O-H, N-H and C-H bonds to alkenes John F Hartwig Reactivity of the coinage metals beyond electrophilic activation of n systems Didier Bourissou, Abderrahmane Amgoune, Maximilian Joost. Fixing nitrogen with iron complexes Jonas C Peters, John S Anderson, John Rittle, Sidney E Creutz. Redox non-innocent nacnac and pyridine-imine chelate complexes of first row metals Peter T Wolczanski, Valerie A Williams, Wesley D Morris, Brian M Lindley, Brian P Jacobs, Thomas R Cundari, Karsten Meyer. Design of new ancillary ligands with nitrogen and phosphorus donors Michael D. Fryzuk, Truman C. Wambach, Fraser Pick, Tatsuya Suzuki. Power curves of buried junction photoelectrochemical cells Daniel G Nocera Determining electronic configuration of diruthenium compounds: Coupling crystallography with magnetic studies Carlos A Murillo Small HOMO-LUMO energy gap favors the chemistry of low valent silicon and transition metals Herbert W. Roesky Phosphorus chemistry and Lewis acid catalysis Douglas W Stephan Werner complexes: A new class of chiral hydrogen bond donorcatalysts for enantioselective organic reactions John A Gladysz Nickel complexes of electron rich PCP pincer ligands: Bond activation and catalysis Warren Piers, Dmitry Gutsulyak, Javier Borau-Garcia, Etienne LaPierre, Masood Parvez. Tantalum and niobium methylidenes Daniel J Mindiola, Keith Searles. Anion complexation and sensing with organoantimony compounds Francois P. Gabbai Copper-oxygen intermediates relevant to metalloenzymes and other oxidation catalysts William Tolman Tuning of the first- and second-coordination spheres in nonheme iron complexes David P. Goldberg, Alison C. McQuilken, Sumit Sahu, Leland R. Widger. Shellfish are inorganic chemists: Characterization and synthetic mimics of marine biological adhesives Erik Alberts, Courtney Jenkins, Heather Meredith, Michael Johnston, Jessica Roman, Chelsey Del Grosso, Michael North, Natalie Hamada, Jonathan Wilker. DNA signaling among proteins with iron-sulfur clusters Jacqueline K Barton PS : I tried to fix the issues with the list, but I couldn't.

Book: The Annotated and Illustrated Double Helix

I have read The Double Helix and wrote a post about it before. Later, I learned that Alexander Gann and Jan Witkowski prepared this book by adding published and unpublished letters, articles and anectodes. It has ~ 300 pages with lots of photos, notes, corrections and extra information that the first book did not have.

If you haven't read the The Double Helix yet, I think you should read this one. If you are one of those people who have read it, you should still read this one since there is much more information in this book.

Since I have already written a post on the book, I don't want to add much on that one. But, it was surprising for me to learn that the publication of The Double Helix caused many problems in scientific society and especially among Watson's friends and colleagues. Crick wrote a final letter to Watson and you can see it in Appendix 4. I think he made it very clear why Watson should not publish the book. To be honest, I now realize that telling everything about a scientific discovery as a simple "story" might not be a great idea.

Update on Clayden's Organic Chemistry textbook "challenge"

As I mentioned in this post, I am trying to finish reading and understanding Clayden's organic chemistry textbook until the end of May 2014. Thanks to spring break, I was able to gain some more speed and today I have finished Chapter 26. Since there are 53 chapters, I thought it would be nice to write about my studies so far. 

Anyway, as you can understand from my blog's header and posts I am way more interested in inorganic chemistry than organic chemistry. But, organic chemistry knowledge is essential in inorganic chemistry too. Firstly, I want to design and synthesize ligands. In fact, I want to prepare a new AND useful ligand on my own. Without knowing the basics and details of organic chemistry, there is no way I can do this. Moreover, without organic chemistry, there is no way that I can even understand and appreciate the use/synthesis of some ligands that are already published. Having finished  Wade's textbook, I realized that I needed to learn more. Also, I know I am not so good at organic chemistry. So, I decided to be better at it with Clayden's.

First of all, my thoughts about the book mentioned in that post haven't changed. I am not an organic chemist, but as a student (the target reader of the book) I still find the book not organized for my educational purposes. It is very common to come across some reagent, reaction or even a functional group in the early chapters without learning anything about them first. Usually, there is a note saying that "...covered in Chapter X." When I compare it to my favorite organic chemistry textbook (Wade's), I still think this book doesn't follow the usual sequence (from simple to difficult). 

I did every single practice problem in the book. Most of the time, I really enjoyed the problems and I am planning to write some blogposts on some mechanisms. My favorite problems and examples are the ones that give or ask you the mechanisms of real drug syntheses. It's great to see that I can understand and design the same syntheses for some drugs. Organic chemistry is really cool! To my surprise, I was able to do ~70% of the problems without much effort. So, I am better than I had expected. Some problems that involve certain agents were really hard for me. Because, if you don't know which one to choose, you will have to go and seek help in tables or chapters. One thing I realized about myself is that I can make some educational guesses, but when it comes to mechanisms I sometimes choose wrong steps although I can draw the right product in the end. I think some problems have more than one routes, and sometimes I am just wrong but lucky. 

I have never done anything about protecting groups at the school, so Chapter 25 took me a while to understand. It's not hard but it was new to me.

Overall (26 chapters), this book is great and I am sure I will always use this book in my future career.

So, now I am ready to go to ACS Dallas and when I come back, I will go on studying. I also decided to read organic chemistry papers too. Maybe they will help me to pick up some tricks. Also I will be able to see more syntheses. Feel free to suggest me readings too.

By the way I did not give up #chempaperaday. In fact, I still read papers but the point of that challenge was that I had decided to read "extra" papers. Right now, I am only reading inorganic chemistry textbooks, books and publications. So, it won't be fair to post those papers.

Notes on Linus Pauling and Magnetic Susceptibility (I)

Linus Pauling is such a big name that whatever text I read, I see his name. He is one of the most important chemists and I truly believe that he deserved at least 3 Nobel Prizes in Chemistry. So, instead of writing a single post about him, I decided to write small pieces as often as I can. After all, there is no way I can tell everything I want to tell about him in one single post. 

I was just reading an inorganic chemistry text and I came across his name at least 10 times in the first 27 pages. Consequently, I decided that it is a good idea to write the most interesting part about him so far.

In early 20th century,  chemists were trying to assign oxidation states to some transition metals and trying to find out the electronic structure of them. They were able to measure the spin. magnetic moments and permanent dipoles of the metal complexes but it was not an easy task to find the correct electronic structure. For example, in 1941, Dwyer and Nyholm prepared several Rhodium complexes and they thought that it was Rh(II). But, they could not understand why the complexes were diamagnetic. Note that Rh(II) has a d7 electron configuration therefore should me paramagnetic and Rh(III) has d6. The answer came in 1960 when it was discovered that the complexes had hydrides and the oxidation state of Rh was three.

Linus Pauling predicted that diamagnetic Ni(II) complexes should be 4 coordinate and at that time this was not observed yet. Later, he also successfully predicted several other geometries for Au(III), Ag(II) and Co(II) complexes. 

He had some unsuccessful predictions too and the most well known of these is his ideas about Vitamin C. Anyway, although his Valence Bond theory is a very successful theory to explain bonding, but for transition metals it was not good enough. I will give the example in the book now.

The magnetic moment of [FeF6]3- is 5.9 Bohr magneton and the moment for  [Fe(CN)6]3- is 1.9 . These suggest that there are 5 and 1 unpaired electrons respectively. In order to explain this, he tried to use Valence Bond Theory and also suggested that the bonding in the first complex was ionic whereas it was covalent for the second complex. 

Better explanations came with Molecular Orbital, Crystal Field and Ligand Field theories. Simply, we now say that F- is a weak field ligand and CN- is a strong field ligand. Therefore, for Fe(III) (d5) in octahedral field the electrons occupy the orbitals like these and give rise to the observed moments:

While at it, I should mention that we can simply calculate the spin only moment by

√n(n+2) 

where n is the number of unpaired electrons. But, because there is also the orbital motion of electrons, another moment is also added to the spin only moments. From my undergrad experience in the tests or practice problems, I saw moments like 2 point something for one unpaired electron etc. So, the experimental values are sometimes very close, sometimes a little bit larger.

So, in theory spin only moments can be summarized in this table:

Number of unpaired electrons	Spin only moment (Bohr magneton)
1	1.73
2	2.83
3	3.87
4	4.91
5	5.92

More on metal-ligand bonding

I don't know (yet) if he was the first to think of a pi-bond between a metal and ligand, but I have just read this:

"Atoms of transition groups are not restricted to the formation of single bonds, but can form multiple bonds with electron-accepting groups by making use of the electrons and orbitals within the valence shell." Pauling, 1939.

It is probably from The Nature of Chemical Bond. I will try to check my book to find the statement.

Alfred Werner and Inorganic Chemistry

According to The Nobel Prize website, nine chemists have been awarded Nobel Prizes in chemistry for their works in Inorganic Chemistry. In 1913, Alfred Werner was awarded the prize for  "... his work on the linkage of atoms in molecules by which he has thrown new light on earlier investigations and opened up new fields of research especially in inorganic chemistry." 

Alfred Werner was born in Mulhausen-Alsace (German land back then) in 1866. When he was in military, he attended some chemistry lectures in a high school. Then, he went on studying chemistry and did his Ph.D. under the guidance of Arthur Hantzsch in organic chemistry! The title of his thesis was "Über räumliche Anordnungen der Atome in stickstoffhaltigen Molekülen" ("On spatial arrangements of atoms in nitrogen-containing molecules"). After a few years, he started to work in University of Zurich where he later accepted Swiss nationality. He was teaching organic chemistry and doing research in stereochemistry of nitrogen-containing molecules, but he became increasingly interested in coordination compounds and inorganic chemistry. He synthesized several ammonia complexes of Cobalt(III). 

In his Nobel lecture, Alfred Werner said:

"During the great era of development of organic chemistry, during which the theory of structure was perfected, the molecular compounds had become stepchildren, and attention only continued to be given to a few of them because they were of practical interest. This neglect can be ascribed to the fact that it was impossible to develop the constitution of these compounds on the same valence principle as the constitution of organic compounds."

Although molecules like NH4+, PCl5 were known, chemists like Kekule, suggested that there could only be one "valence" (oxidation state) of a given element. For example, Kekule suggested that PCl5 is in fact PCl3.Cl2 . This dot notation is still used although it does not give any structural information (CuSO4.5H2O, IrCl3xH2O etc.). 

Werner was both a great theorist and an experimentalist. He was certain of the existence of the isomers of his metal complexes. So, he went on drawing the possible isomers for a six-coordinate model complex and finally suggested that the complexes had octahedral geometries. He supported his suggestion by some observations.

images are from this free review article: http://web.campbell.edu/faculty/mbwells/ftp/courses/chem331/inorganic%20news/werner_history.pdf

Of course, like Kekule, there were other chemists that thought the oxidation state is fixed and the bonding had to be like these:

(You can find more on the discussions why these were wrong here or here in his Nobel lecture.)

Finally, he was able to introduce a new geometry, isomers and the possibility of having a different Hauptvalenz (oxidation state) than Nebenvalenz (coordination number). He also made some contributions to the final "shape" of the periodic table. He arranged the known elements of his time and left space for lanthanides and actinides understanding that they were "different" without knowing any quantum chemistry.

In almost every inorganic chemistry textbook and article on inorganic and coordination chemistry, you can see Alfred Werner's and his complexes' name repeatedly (Werner Complexes, anti-Werner Complexes etc.) and I think it is right to call him as the "father of modern inorganic/coordination chemistry." 

  

He wrote almost two hundred articles and two books; Lehrbuch der Stereochemie ("Textbook of Stereochemistry") and Neuere Anschauungen auf dem Gebiete der anorganischen Chemie ("New Ideas in Inorganic Chemistry"). You can read them in German both online and free here and here. Lehrbuch der Stereochemie was dedicated to his Ph.D. advisor Arthur Hantzsch.

On The Chelate Effect

"Metal chelates are inherently more stable than closely related nonchelate complexes."[1] This statement simply explains that the metal-polydentate ligand complexes are thermodynamically more stable than a metal-monodentate ligand complex (provided that the donor atoms are the same). I have seen several tables that shows this effect in a quantitative way like the one below: (It is adapted from the book I have just finished)

But, as explained in this paper (unfortunately, not free), chelate effect "decreases with the increase in concentration of the ligands and can become zero, or even negative, as observed in practice."

Since the article is not free, I think I am not able to copy and paste the equation derived to explain the statement above or the tables that show how chelate effect became negative with increasing concentration. I don't know much about this copyright thing, so I'll pass.

Anyway, I think it is important to know that concentration of the ligand has an effect on it. Until a few weeks ago, I did not know it. If you are interested in metal chelates, there is a FREE and detailed study of them by Arthur E. Martell here. I hope I will read it very soon.

[1] Dwyer, F.P.; Mellor, D.P. Chelating Agents and Metal Chelates. 1964. New York. Academic Press. pp 42

Book: Metal Chelation Principles and Applications

I think it is a very short, simple and good book to read in a few hours if you are interested in metal chelation. There are 8 chapters and my favorite chapters are Properties of Metals and Thermodynamic Aspects. These two chapters gave me a few blog post ideas and I hope I can finish them in this week.

Point Group Assignment (flow chart)

This is a flow chart to help to assign point groups for molecules and I think it is way better than my original hand written method in my symmetry series. I wanted to see how it looks like. It is my first "infographic." I will do better I promise.

I created this infographic on easel.ly and the flow chart is adapted from Inorganic Chemistry textbook by Miessler and Tarr.

Chelate/Chelation

Well, I know what a ligand, chelate or chelation is, but I have never wondered how I can describe it to someone who does not know any chemistry. So, I tried to find out the roots and the first use of these terms. 

According to wikipedia and many other websites, articles and books, the term "chelate" was first used in chemistry in 1920 by Gilbert Morgan and D.K. Drew. I took the quote from the wikipedia page: (A paper I am reading right now says that the word "ligand" was first used by Stock in 1917. But, it says the description of "chelating" was introduced by Drew and Morgan.)

"The adjective chelate, derived from the great claw or chele (Greek) of the lobster or other crustaceans, is suggested for the caliperlike groups which function as two associating units and fasten to the central atom so as to produce heterocyclic rings."

And below is the article. Unfortunately, it is behind a paywall. 

http://pubs.rsc.org/en/content/articlelanding/1920/ct/ct9201701456#!divAbstract

Obviously, I had to look for what "chele" (chela) looks like:

image source: http://upload.wikimedia.org/wikipedia/commons/0/0b/Fiddler_crab.jpg

I also found some useful definitions for some terms here in the same article above although I've never heard some of them:

Book: Introduction to Metal Pi-Complex Chemistry

As the title states clearly, this book is about the metal and pi-complex interactions. It starts with the history of metal pi-complexes. The first metal pi-complex was Zeise's Salt. But, until the characterization of ferrocene, it did not receive much attention. 

The following chapters include the preparation, reactions, spectroscopic and magnetic properties of the complexes. There is a very short chapter on Crystal Field Theory, Valence Bond Theory and Molecular Orbital Theory too. 

What I like the most about the book is that it provides very simple methods for the preparation and reactions of these complexes. There are around 20 different reactions of ferrocene and ferrocene derivatives. 

The book I have is a 1970 edition and it looks like there is a 1995 edition on amazon. It's worth buying.

image source: http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---F/Ferrocene.-kaJ.htm