Wednesday, July 27, 2011


Iron has so much history that I may have to make a little hash tag label for it like I did for carbon with bloghetti carbonara. There is just too much for one blog post.

In my last year in college at Madison, I took a graduate level course (Chem 714) called Organometallic Chemistry of the Transition Elements. I may have been the only undergraduate in the course. One of the reading assignments was called "The Iron Sandwich. A Recollection Of The First Four Months" by Geoffrey Wilkinson (Journal of Organometallic Chemistry 1975, 100, 273-278).

Wilkinson narrates the story of how he deduced the correct structure of ferrocene, shortly after its incorrect structure was first published. The work was seminal and led (in part) to his sharing the 1973 Nobel Prize in Chemistry along with E. O. Fischer of Munich.

Here he sets the stage (annoying footnotes are mine):
In early September of 1951, I arrived at 12 Oxford Street, Cambridge, Mass., as a new Assistant Professor in the Harvard Chemistry Department. I owed my appointment largely to my nuclear background. Harvard had originally intended to appoint a tenure member in nuclear chemistry, a plan which did not materialize, and had settled for myself and an Instructor, Dick Diamond, a newly graduated Ph.D. from Seaborg's laboratory in Berkeley. I was given a laboratory in the Mallinkrodt Laboratory, and went to work collecting chemicals and apparatus and built myself a small vacuum line.*
* By vacuum line, Wilkinson means a glass tube contraption having numerous valves and fittings designed to allow working in the absence of air. Organometallic chemistry included many interesting chemical species which reacted with atmospheric oxygen- see for example the contemporaneous catalysts Ziegler was exploring an ocean away.

Wilkinson went on to describe adjusting to Harvard faculty life in a chatty way before focusing on his eureka moment:
So the story for me actually began on Friday, I think 30th January, 1952. I normally went into the Departmental Library lateish on Friday afternoons, and as usual I picked up Nature, in which I found the celebrated note by Kealy and Pauson.*  On seeing the structure...I can remember immediately saying to myself  "Jesus Christ it can't be that!"

*T.J. Kealy and P.L. Pauson, Nature, 168 (1951) p. 1039.
Wilkinson intuited that the published structure was wrong because it was inconsistent with any other existing iron compound. The published structure (above) implied that a central iron latched onto just one carbon of each five-sided carbon ring (cyclopentadienyl). In a flash of insight, Wilkinson immediately sketched what was later redrafted for publication as:
He proposed the two hourglass-shaped structures differing only in how the five-sided rings (the bread slices of the iron sandwich) aligned with each other. He quickly went on to show that other sandwich structures existed for other metals, discovering a new genus of compounds now generically called metallocenes.

One irony in this story is that Harvard failed to offer Wilkinson tenure after he did this prize-worthy work, despite the widespread acclaim it engendered during his time there.  Harvard either didn't recognize the importance of his work or, as I suspect, he made some academic enemies there.

I recently found myself at an informal meeting of chemists and a story regarding Harvard Chemistry came up: "Yeah, Harvard--they never tenure anybody" a friend said.  After sixty years, they haven't shaken that reputation. To many, Harvard broke the code of not rewarding merit.

Wilkinson's subsequent career certainly didn't suffer.  He went on to chair the Department at Imperial College in London. He wrote an outstanding textbook used by generations of chemists. He discovered "Wilkinson's catalyst" (something that became near and dear to me).

The tenure story gets better when Harvard's Robert Burns Woodward is considered. Woodward is a co-author on the original ferrocene paper with Wilkinson but did not share that prize with Wilkinson. Woodward, perhaps the greatest American organic chemist ever, had previously won a Nobel Prize alone and probably would have shared another--had he lived--but not this one. Wilkinson thought that Woodward had had the same flash of insight as he. But did he? You can read the story for yourself here,* retold by Professor Roald Hoffmann of Cornell University.  Hoffmann knew Woodward. They shared a Nobel Prize together. But that's another story worthy of bloghetti carbonara.
*Warning: Hoffmann invokes Rashomon, and quite aptly I think.

1 comment:

  1. The names Woodward-Hoffmann are so entwined in my mind that I forgot that he (Woodward) did not in fact share the 1981 prize with Hoffmann (Woodward died in 1979).