Category: Essays in Angewandte Chemie

FERROCENE: IRONCLAD HISTORY OR RASHOMON* TALE?

Pierre Laszlo and Roald Hoffmann

A critical stance is essential to science. Proving other people wrong is a favorite private and public satisfaction — there is nothing some people like better. But, excess zeal discounted, doubt serves as a powerful impulse to the advancement of knowledge. We document it here with the discovery of the structure of ferrocene, a story which also plays up the virtue of the spoken word. [1] We base it on various published (and most fragmentary) accounts, supplemented with some very helpful correspondence from colleagues.

Just as with ferrocene, 1 the formula first written for diborane B2H6 was orthodox, in conformity with the usual paradigmatic rules regarding molecular structure. And it was wrong. Correcting the mistake showed an extremely unusual bonding picture for the molecule. Just as in the ferrocene case, it opened up a whole new chapter of chemistry, later recognized with the award of a Nobel prize to William N. Lipscomb in 1976 for “his studies on the structure of boranes illuminating problems of chemical bonding.”

I shall highlight here only a few episodes from the diborane story. In 1937, a former student of Linus Pauling, Simon H. Bauer – incidentally he is still active in research at Cornell, at the age of 88 – applied the technique of electron diffraction, a tool which he had learned to use at Caltech with Pauling, to diborane. He found and he reported a structure analogous to that of ethane, which therefore he wrote as H3B-BH3. 2 In 1942, Bauer reiterated his contention of the ethane-like structure for diborane. 3 At the same time of the early 1940s, H.I. Schlesinger, a chemistry professor at the University of Chicago, was also working on boron compounds. One of the reasons was his involvement in the Manhattan Project: it was thought that an isotope separation could be devised for uranium using such derivatives. In any case, Schlesinger was very much interested in the structure of diborane.

Science often advances upon willful transgression of a seeming interdiction. Examples which leap to a chemist’s mind are noble gas compounds, strained hydrocarbons such as tetrahedrane, activation (by organometallics) of even methane, and, to mention just one brilliant, more recent achievement, inclusion of an allene within the confines of a six-membered ring while preventing its conversion into a benzenoid. Such feats put all the cunning of a scientist into coaxing and, yes, coercing the system at hand to obey instructions from one’s daring imagination. As always, it is hard. Not for nothing is our playroom called a laboratory. And when the task is done and the time arrives to convey to others (who might not be privy to the anguish of the work) all that struggle and the majesty of the achievement, the scientist quite naturally lapses into metaphor. One such, founded in male 19th century language as much as in history, is some more or less prurient variant of “Unveiling the Secrets of Nature.” Another, evoking the thorny, twisted path to understanding and the long hours of toil in the laboratory, is “Wrestling with Nature.”

Chemists are legitimately distressed by the chemophobia of the public. One of its manifestations (hardly the only one) is the stereotyped presentation of a chemist as an amoral character, having sold his soul to the Devil. The implicit sin is more than Faustian, for the betrayal is not only personal, but that of humanity. Fritz Haber is often this scapegoat.

Is this stereotyping deserved? And might we, collectively and individually, do something about it? We approach the issue here by way of an attentive reading of a selectioni of the literary pieces featuring Haber, whether under his own name or in transparent disguise, and of recent biographies of Haber.