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Published by
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A GUIDE TO CHALCOGEN-NITROGEN CHEMISTRY
Copyright © 2005 by World Scientific Publishing Co. Pte. Ltd.
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Preface
The quintessential chalcogen-nitrogen compound tetrasulfur tetranitride,
S N , was first detected by Gregory in 1835 just ten years after the
4 4
discovery of benzene. Its unusual structure, like that of benzene, was not
elucidated for over 100 years. The application of diffraction techniques
revealed the unusual cage arrangement with two weak cross-ring sulfur–
sulfur interactions. The details of the electronic structure of this
fascinating molecule are still a matter of debate today.
Pioneering work in Germany, especially by the groups of Becke-
Goehring, Weiss and Glemser, in the middle of the previous century
uncovered a rich chemistry for inorganic sulfur–nitrogen systems. Their
early efforts were notable because of the unavailability of many modern
physical techniques for structural characterization that are commonplace
today. The book by Goehring entitled “Ergebnisse und Probleme der
Chemie der Schewfelstickstoffverbindungen” deserves special mention
for the stimulus that it provided to subsequent workers in the field.
The polymer, (SN) , was first obtained in 1910 and its metallic
x
character was noted. However, it was the discovery in 1973 by Labes
that a polymer comprised only of non-metallic elements behaves as a
superconductor at 0.26 K that sparked widespread interest in sulfur-
nitrogen (S–N) chemistry. A year earlier Banister proposed that planar S-
N heterocycles belong to a class of “electron-rich aromatics” that
conform to the well known Hückel (4n + 2)(cid:140)-electron rule of organic
chemistry. This suggestion, which was based on simple electron-
counting concepts, provided an additional impetus for both experimental
and theoretical investigations of S–N systems. The classic book in this
field “The Inorganic Heterocyclic Chemistry of Sulfur, Nitrogen and
v
vi Preface
Phosphorus” by Heal covered developments up to the end of the 1970s.
This opus contributed authoritative insights into the fascinating
chemistry of S–N compounds. It used a descriptive approach that drew
attention to the many facets of the synthesis, structures and reactions that
were poorly understood at that time.
In the first chapter of his book Heal states:
“Indeed, the reaction chemistry of these substances (i.e., SN
compounds) deserves to rank with that of boranes for novelty and
interest”.
In the past twenty-five years the field of S–N chemistry has reached
maturity as a result of contributions from many countries, notably
Germany, the U.K., Canada, Japan and the United States. The
combination of structural studies, primarily through X-ray
crystallography, spectroscopic information and molecular orbital
calculations has provided reasonable rationalizations of the structure-
reactivity relationships of these fascinating compounds. The unusual
structures and properties of S–N compounds have attracted the attention
of numerous theoretical chemists, who continue to address the “aromatic’
character of binary S–N systems. Interfaces with other areas of
chemistry e.g., materials chemistry, organic synthesis, biochemistry and
coordination chemistry have been established and are under active
development. For example, materials with unique magnetic and
conducting properties that depend on intermolecular chalcogen–nitrogen
interactions between radical species have been designed. Some carbon-
nitrogen-sulfur heterocycles exhibit magnetic behaviour that is of
potential significance in the construction of organic data recording
devices. In another area of materials chemistry, polymers involving both
S–N and P–N linkages in the backbone have been used as components of
matrices for oxygen sensors in the aerospace industry. In a biological
setting, S-nitrosothiols (RSNO) have emerged as important species in the
storage and transport of nitric oxide. As NO donors these sulfur–nitrogen
compounds have potential medical applications in the treatment of blood
circulation problems. In a different, but fascinating, context, thionitrite
anions [S NO]- (x = 1,2) are implicated in the gunpowder reaction
x
through an explosive decomposition.
Preface vii
The chemistry of selenium– and tellurium–nitrogen compounds has
progressed more slowly but, in the last ten years, there have been
numerous developments in these areas also, as a result of the creative
contributions of both inorganic and organic synthetic chemists.
Significant differences are apparent in the structures, reactivities and
properties of these heavier chalcogen derivatives, especially in the case
of tellurium. In addition, the lability of Se–N and Te–N bonds has led to
applications of reagents containing these reactive functionalities in
organic syntheses and, as a source of elemental chalcogen, in the
production of metal chalcogenide semi-conductors.
In addition to providing a modern account of developments in
chalcogen–nitrogen chemistry, including a comparison of sulfur systems
with those of the heavier chalcogens, these interfaces will provide a
major focus of this monograph. As implied by the inclusion of “A Guide
to ….” in the title, it is not intended that the coverage of the primary
literature will be comprehensive. Rather it provides an overview of the
field with an emphasis on general concepts. Each chapter is designed to
be self-contained, but there are extensive cross-references between
chapters. By the use of selected examples, it is hoped that a reader, who
is unfamiliar with or new to the field, will be able to gain an appreciation
of the subtleties of chalcogen–nitrogen chemistry. A complete list of
review articles is given at the end of Chapter 1. Key references to the
primary literature are identified at the end of each chapter for the reader
who wishes to pursue an individual topic in detail. The literature is
covered up to mid-2004. Apart from two notable exceptions, the
coverage of sulfur-nitrogen chemistry in standard inorganic (and organic)
chemistry textbooks is sparse and usually limited to brief comments
about the neutral binary compounds S N , S N and (SN) . Those
2 2 4 4 x
exceptions are the second edition of “Chemistry of the Elements” by
N.N. Greenwood and A. Earnshaw (Butterworth-Heinemann, 1997) and
the 34th edition of “Inorganic Chemistry” by Hollemann–Wiberg
(Academic Press, 2001), which devote 26 and 14 pages, respectively, to
this topic. It is hoped that the information in this book will be helpful to
those who wish to go beyond the standard textbook treatment of various
aspects of this important subject.
Acknowledgements
The first draft of this book was written during the tenure of a Killam
Resident Fellowship at the University of Calgary in the fall term, 2003.
The author is grateful for the financial support that provided release from
other duties in order to focus on this project.
Subsequent drafts were composed after the receipt of input from
various international experts on individual chapters in their areas of
expertise. The author acknowledges, with gratitude, helpful (and
encouraging) comments from the following individual scientists:
Professor R. T. Boeré (University of Lethbridge, Canada), Professor N.
Burford (Dalhousie University, Canada), Dr P. Kelly (Loughborough
University, England), Professor R. S. Laitinen (University of Oulu,
Finland), Professor Dr. R. Mews (Universität Bremen, Germany),
Professor R. T. Oakley (University of Waterloo, Canada), Professor J.
Passmore (University of New Brunswick, Canada), Professor K. E.
Preuss (University of Guelph, Canada), Dr J. R. Rawson (University of
Cambridge, England), Professor H. B. Singh (Indian Institute of
Technology, Bombay, India), Professor I. Vargas-Baca (McMaster
University, Canada). Their perceptive suggestions have enhanced the
quality and accuracy of the final version of this monograph substantially.
Nevertheless, there are undoubtedly shortcomings in the form of errors
or omissions for which the author is entirely responsible.
Special thanks are accorded to Dr Dana Eisler (University of
Calgary), who not only prepared all the structural drawings, figures and
schemes, but also diligently proof-read the penultimate version of the
manuscript. Professor Richard Oakley provided the idea and created the
graphics for the design on the cover page. This representation of
ix
