* BARTLETT, Neil
British chemist                .
Born Sept. 15, 1932, Newcastle-upon-Tyne, Eng-
land

W HILE INVESTIGATING the fluorides of the
  platinum metals, Bartlett in 1962 prepared
the first chemical compound of a noble gas. The
noble gases were discovered by Lord Rayleigh
and by Sir William Ramsey and his co-workers
in the 1890s. The first gas to be discovered and
the most abundant, argon, was quickly subjected
to intensive chemical and physical examination
and found to be chemically inert. Henri
Moissan, the first to prepare fluorine, attempted
to prepare an argon fluoride in 1895, and his
failure impressed him and his friend Ramsey
with the inertness of the gas. Several perceptive
chemists pointed to the greater likelihood of the
heavier (and much rarer) gases, krypton and
xenon, entering into chemical combination. L. C.
Pauling, in particular, suggested in 1933 that
xenon and krypton fluorides should be prepara-
ble, and in the same year an abortive attempt
was made to prepare a xenon fluoride. The
failure to sustain claims to noble gas com-
pounds, together with the inability of experienced
investigators to carry out the most favorable
syntheses, contributed to an acceptance of the
complete inertness of the gases, but it was
probably not the most important contributing
factor. Undoubtedly, the popularity of the
simple electronic theories of valence, which em-
phasize the special stability of the noble gas
configurations, had a major influence. The scar-
city of the most favorable gas, xenon, and the
instability of radon, which should be the most
chemically active gas, were also contributing
factors.

Bartlett started his independent research with
the intention of better defining the factors which

limit the oxidation states of the elements. The
noble metals, in particular, attracted his interest
because of the promise of a greater range of
oxidation states. Investigation of these elements
also promised to be of value in his concern to
define more clearly the relationship of the ligand
geometry of molecules and crystals to the
valence electron configurations of the central
atom. The synthetic work, which involved fluo-
rides and oxyfluorides, was therefore accom-
panied by structural studies. This combination
was to prove vital to the discoveries which
followed.

The compound of prime importance in the
discovery of xenon chemistry was investigated
initially in the belief that it would prove to be
an oxyfluoride of 6-valent platinum. The com-
pound was first observed as a sublimable red
solid produced when platinum or platinum com-
pounds were treated with fluorine in glass ap-
paratus at moderate temperatures. The red solid
was marked by great chemical reactivity, and
it proved necessary to develop special techniques
to analyze it. In 1961 Bartlett, with D. H. Loh-
mann, established the empirical formula as
PtO.,Fs. Extensive chemical and physical char-
acteiization clearly indicated the compound
to be a salt, dioxygenyl hexafluoroplatinate,
O,+[PtFs]-. This was the first example known
to represent either of the ions. It was particu-
larly remarkable for its oxidized oxygen cation.
This formulation implied that the molecular
fluoride, platinum hexafluoride, which had been
reported by Bernard Weinstock and J. C. Maim
in 1958, should be capable of oxidizing molec-
ular oxygen. This proved to be so, the two
gases combining spontaneously at ordinary tem-
peratures and pressures:

O;Ld + PtF,(g) + O,+ [PtFsl- (s)

Although the salt formulation had seemed ap-

propriate early in the research, it posed the
difficulty that the electron affinity of platinum
hexafluoride,

AE(PtFs(g) + e + PtFs-(g) 1

needed to be greater than -160 kcal/mole (that
is, approximately twice the value for atomic
fluorine or atomic chlorine), so that oxidation
of molecular `oxygen should proceed spontane-
ously. The proof of the salt formulation, there-
fore, pointed to platinum hexafluoride as the
most powerfully oxidizing molecular species
recognized so far. Bartlett noted that the ioniza-
tion potentials of the heavier noble gases
(xenon, 12.2 ev; radon, 10.5 ev) were as low
as, or lower than, molecular oxygen (12.2 ev),
and hence he concluded that these gases should
also be oxidizable. In his investigations in 1962


xenon gas proved to be as easy to oxidize as
molecular oxygen. The orange-yellow solid
formed in the spontaneous gas-gas reaction
was  designated  xenon hexafluoroplatinate,
Xe+ [PtF,] -. The work on xenon hexafluoro-
platinate stimulated investigation of the other
noble gases in a number of laboratories, and
compounds of krypton, xenon, and radon are
now well characterized chemically and physi-
cally. Major consequences of the discovery of the
chemical activity of the heavier noble gases have
been the development of a greater awareness of
the limitations of simple valence theory and
the focusing of attention on the nature of bond-
ing in these and related compounds.
Bartlett was an undergraduate and graduate
student at King's College, Newcastle-upon-Tyne,
from 1951 to 1957; his Ph.D. work was done with
P. L. Robinson. He was senior chemistry master
at the Duke's School, Alnwick, for 1 year, and
in 1958 moved to the University of British
Columbia, where he served on the faculty for
8 years. In 1966 he was appointed a profes-
sor of chemistry at Princeton University. Among
the honors awarded Bartlett were the 1962 Cor-
day-Morgan Medal and Prize of the Chemical
Society of Great Britain, the 1965 Research
Corporation Award, and the 1%5 E. W. R.
Steacie Prize.
For background information see INERT GASES;
VALENCE in the McGraw-Hill Encyclopedia of
Science and Technology.            Cl