APR | 4 1993

CHAPTER XIV

AWARD ADDRESS*
NEIL BARTLETT, University of California at Berkeley, Berkeley, California

ROBERT A. WELCH AWARD — NEIL BARTLETT

(G. T. Seaborg: "I have the honor to present Dr. Neil Bartlett, internationally
renowned scientist, a man who has conducted meritorious research in chemistry. He
is being recommended on the basis of his synthesis of compounds of the noble gases
and the consequent opening of broad new fields of research in inorganic chemistry”.

Roger J. Wolfe: "I, Roger J. Wolfe, on behalf of the trustees of The Robert A.
Welch Foundation, confere upon you Dr. Neil Bartlett the third Robert A. Welch
Award in Chemistry on the basis of your meritorious chemical research. It is my
pleasure to hand you a check in the amount of your award, and a certificate endorsed
by the trustees and officers of The Robert A. Welch Foundation. Please accept my
most sincere congratulations".

W. O. Milligan: Dr. Bartlett may I add the congratulations of all of us in this

room, including my own.)

Dr. Bartlett*: Ladies and Gentlemen, Friends. I am, of course, overwhelmed,
as you might imagine, by this great honor, but I have to say, immediately, that I
recognize myself as being an exceedingly luckly fellow. No matter what the merits
of my case may, or may not have been, I have clearly had persuasive proposers and
they have obviously labored mightily on my behalf. I am indeed grateful to these

unknown supporters for their efforts.

Like Dr. Lowdin, I am under some pressure to be brief. Although it has been a
remarkable, absorbing day it is late and I must therefore proceed quickly with my
talk. I would like to talk to you about a little bit of research — in fact about the
research which has been recognized by this award. I believe that the story will also
illustrate some of the points that Professor Lowdin has made earlier.

*

In 1956 I was a graduate student, and | was supposed to be working on sulfur

compounds and in particular on sulfur fluorides, but I was a curious fellow and for a

complicated set of reasons I found myself, late in that year, working on platinum

*An address presented before "The Robert A. Welch Foundation Conferences on
Chemical Research. XX. American Chemistry—Bicentennial", which was held in
Houston, Texas, November 8-10, 1976.

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compounds. By sheer chance I made, I believe it was on November 5, 1956, a readily
volatile fluorine-containing compound of platinum. This excited me because there
were, at that time, no such compounds known. Although I was drawing my graduate
work to a close this was clearly something that I should look into as soon as possible.
I did try to look into it immediately but the problem proved to be too big for the few
weeks remaining in my graduate program. So, I kept it very much in mind, and when
the opportunity came of moving to the University of British Columbia in Vancouver,

Canada, I took this problem with me.

I was fortunate in Canada in being supported by the National Research Council
of Canada, and I have to say that I felt remarkably free to do what I liked to do, and I
have to say also that today I have a sense that not too many people have the kind of
freedom that I had in Canada at that time. Of course I wrote research proposals, and
as you might expect, I did not include this problem, because I didn't know what the
material was and had no good theoretical basis for proposing it for a research.
Nevertheless, I took the problem on. I didn't worry about that, because I wasn't
constrained to work solely on the problems that I said I would work on. I want to
acknowledge that at this time I also had support from the Research Corporation
(which is a smaller foundation that the Welch Foundation, and supports science in not
only the United States but in Canada also). I benefited enormously from the Research
Corporation support at the Univeristy of British Columbia. Although the money was
not great in quantity ($3,000 or so) it did not constrain me to work on tightly defined
lines and along with the National Research Council support it was possible to tackle
the problem in a thorough manner. It took two or three years to get to the heart of

the matter.

This platinum compound is a remarkable material. When we put it in water, for
example, it liberated all manner of things, including light, ozone, platinum metal and
other decomposition products. Within three years, my first Ph.D. student, Derek
Lohmann, and I had the problem pretty well licked. We knew the chemical
composition of this material, and it turned out to have the chemical formula PtF.O..
It was, in fact, a salt of the dioxygeny! cation and the hexafluoro-platinate anion —
both new ions. Platinum hexafluoride, you see, was the most powerful oxidizer that
anyone had ever come across. It had oxidized the oxygen molecule." Here we were
then, at the end of 1961.

I talked to my chemist colleagues, at The University of British Columbia, about
this material and they were most interested, but I detected an undercurrent. |
thought maybe some did not really believe my conclusion, because I was asked
occasionally if I was sure that everything fit the ionic formulation. We had been at

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great pains to prove the 0, "PIF salt and all of the properties, physical and
chemical fit splendidly. But these doubters were a challenge and I had to respond to
them. I had to find a more dramatic case than the oxidation of oxygen, to win over
the doubters. It occurred to me early on that I should try to oxidize helium. On
reflection, I realized that this would be impossible, because I also knew that the
platinum hexafluoride gas would not even oxidize nitrogen, because that's the way we
had been making our compound. We had been carrying platinum hexafluoride in
nitrogen gas. Since helium is very much harder to oxidize than nitrogen, I dismissed
helium from further thought. It wasn't until February 1962 — I don't unfortunately
know the exact data, but it took a gestation period of 6 weeks to 2 months from the
O,Ptr, solution — when the next important event occurred. I was preparing a
lecture; I was looking up something — exactly what I have forgotten, and as I turned
the pages of the text book I noticed a diagram which illustrates a relationship which I
should have remembered, because I learned it in high school. It reminded me that the
ionization potentials of elements depend on atomic number and that the heavier
elements have low ionization energies. I immediately knew what to do — look up the
ionization potentials of the noble gases. If you trace the ionization potentials down
the noble gases from helium through to radon, you see that the ionization potential
falls from about 24 eV (an enoumous amount of energy) down to a little over 10 eV
(less than that of molecular oxygen) by the time you get to radon. Radon was
obviously the thing to oxidize, but only Glenn Seaborg and his expert colleagues can

handle that element, because it is an alpha emitter.

The next choice was xenon, and by sheer concidence xenon's ionization potential
was only | kcal per mole away from that of oxygen. With the thought complete, I
rushed out of my office and tried to find a colleague of mine who was an expert in
matrix isolation spectroscopy. He used to use noble gases ali the time, and knew
their behavior in detail. By chance he was in the corridor outside my office. So, I
rushed up and asked him, "Do you have some xenon?" He was in conversation with
another colleague; he turned and said, "why do you want xenon?" [ responded, "I want
to oxidize it". In fact, he laughed. I don't blame him, but it immediately confirmed
my suspicion that I had not convinced him that platinum hexafluoride was the most
powerful oxidizer of all.

a

I ordered some xenon. By this time my first student had left me and I had two
inexperienced students with me, so I had to get down to it and do the experimental
work myself. So, I made a very simple apparatus out of glass and quartz, and set to
mix the xenon with platinum hexafluoride. I finally had everything ready by a Friday
evening, in March. In fact, I have checked my notebook and it was around about 8:00

p-m. and I was worrying about my poor wife, whom I imagined would be wondering

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where in the devil I had got to. My students had crept away, but I had everything set
up. It was a very simple apparatus with the red platinum hexafluoride gas separated
from the xenon gas (which is a colorless gas) by a very thin glass diaphragm. I had
arranged with a magnet to lift some little spheres of nickel through the xenon gas, so
as to smash the diaphragm in order to mix one gas with the other. As I broke the
diaphragm, there was an immediate reaction between the xenon gas and the platinum
hexafluoride gas. It was essentially the same kind of reaction as had occurred some

weeks earlier when I had mixed platinum hexafluoride with oxygen.

So I rushed out of the laboratory to spread my news — and there wasn't a soul

there! Well, there we are it was for me a tremendously exciting discovery.

Let me now mention another matter. Many people ask, "what use is it?" Tama
little embarrassed by that question. I won't labor the point because I am convinced,
as convinced as I am that I am standing here, that in time, this discovery will have
practical value. We already know that radon can be scrubbed from air by xenon salts
which oxidize the radon. Dr. Lawrence Stein at The Argonne National Laboratory has
also shown that dioxygeny! salts take radon out of the air and liberate oxygen in the
process. Radon is a natural contaminant of the air in uranium mines. There is,

therefore, even here a possibility of practical application.

I know that basic research will pay off. It's important that we should think in
the long term and I am afraid that today we are thinking a little too much in the short
term, a little too much in the short term about everything. However, I won't harp on

such serious matters now.

To end, Jet me tell you a story involving a Great British scientist (since | am
British, I must use a British example). The scientist is Michael Faraday. Michael
Faraday, was a great experimentalist, and a man of humble beginnings, but a man of
great perception and great experimental skill. In 1831, he discovered the principle of
the dynamo and a few years later the Prime Minister of that time, Sir Robert Peel
learned of this remarkable discovery of Faraday's. He went along to Faraday's
laboratory at the Royal Institution in Albemarle Street in London, and asked to see
the little device that Faraday had built. Faraday showed itato him, and Peel said (and
you all know what is coming), "And of what use is it?" And Faraday said, "I know not.
But I wager that your government will eventually tax it." Long after, when Faraday
and Peel were both dead, the electrical power industry became large enough to
attract the eye of the Treasury and was indeed taxed.

I see a glint in W.O's eye, I had better quit the stage. I thank you for listening,

and give my thanks and best wishes to The Robert A. Welch Foundation.
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Dr. Neil Bartlett