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Chatt, Joseph

CHATT, JOSEPH

(b . Hordern, County Durham, England, 6 November 1914;

d. Hove, Sussex, England, 19 May 1994), inorganic and organometallic chemistry of transition elements, nitrogen fixation.

Joseph was one of the originators of the field of transition-metal organometallic chemistry and was an innovator in the areas of synthesis, understanding electronic effects, and the study of the mechanisms of the reactions of transition-metal compounds. In nitrogen fixation, his group prepared more novel dinitrogen complexes than any other, into the early 2000s, and he led the way in building inorganic models for the mechanism of biological nitrogen fixation.

Education and Early Career . Joseph Chatt, eldest son of Joseph and M. Elsie Chatt, began his education in a very inauspicious manner, in the village school of Welton, not far from Carlisle in the northwest of England. He stayed there until he was fourteen. This school was very conventional, teaching no science as such, and as his father was a farmer, he received little encouragement to study science at home. However, his uncle was the chief chemist in a steelworks near Newcastle upon Tyne, and Joseph learned some basic chemistry and physics on his holiday visits there. His home did not have an electricity supply, but when his uncle sent him a book on electricity and magnetism, Chatt fitted up his bedroom with an electric light powered by a dichromate cell and switched the light on and off from the door by raising and lowering an electrode using a piece of string. Not only did his uncle inspire an interest in science, but the area where he lived, Caldbeck Fells, is comprised of many old and metalliferrous rocks. Chatt searched out rock types, an interest that stayed with him. After moving on to secondary school, he came into contact with a chemistry teacher who encouraged him in many ways, not least in inorganic analysis to determine what metals his rock samples contained, but also in other branches of chemical science, and Chatt used this disinterested help to explore chemistry for himself, in a way that would not be permitted on grounds of safety to young chemists in the early 2000s. Chatt claimed to be the last person to have observed the direct reaction of sodium metal and concentrated sulphuric acid, because it is unlikely that anyone since would have dared to try such a potentially dangerous experiment.

Not only was Chatt an unusually highly motivated pupil, but the masters at his secondary school, the Nelson School at Wigton, were very perspicacious. They realized that this pupil was exceptional, even taking into account that he had arrived at the school three years older than the usual intake. He matriculated in about two years rather than the normal five. Although the family’s circumstances were straitened, he won scholarships sufficient to allow him to study at Cambridge University, something that his farming family would never have envisaged. He obtained a place at Emmanuel College Cambridge through the efforts of his mathematics master, who though the university already had its formal quota of new students, personally made a tour of the individual colleges until he found one that was prepared to accept his exceptional pupil.

Chatt would have started his studies at Cambridge in October 1934, but he was unable to do so until he had passed the then-obligatory examination in Latin, which he had not studied before. With yet more help from his secondary school, he passed this exam and entered the Cambridge in January 1935. He obtained his PhD in the summer of 1940, when World War II had been in progress for about a year.

During World War II, Chatt was unable to follow his academic interests. His 1940 appointment to an academic post at St. Andrews University, Scotland, seems to have lapsed completely. He never took it up, and instead performed various functions related to the war effort. The government authorities dictated these, and none of them seems to have been very appropriate. His weak ankle, which troubled him for the whole of his adult life, clearly prevented him from active service in the armed forces. However, Chatt was obliged to do as he was directed in the national interest, and he finally finished as chief chemist in a factory concerned mainly with the production of alumina. Once the war was over, he resigned and went to the Imperial College of Science and technology in London as an ICI (Imperial Chemical Industries) Fellow.

Coordination Chemistry around 1940 . When Chatt began his research work, chemistry research was almost entirely concerned with organic chemistry. Inorganic chemistry, which had interested him because of the multitude of elements he had detected in his rock samples, was regarded as a finished subject. Textbooks on inorganic chemistry were generally compendia of preparations, colors, and physical properties. Organometallic chemistry was a subject of limited interest and was restricted to elements such as silicon and magnesium, which are main-group elements. There was skepticism as to whether transition-metal organometallic compounds would be stable enough to exist under ambient conditions. Very few academics were interested in the subject, but one of the few was Frederick G. Mann, whose lectures Chatt admired. Mann was interested in the nature of various types of chemical bond and believed that information on their quality might be derived from a parameter called the parachor, related to the dipole moment of a molecule, itself a measure of charge separation. The measurement of the parachor required the preparation of solutions in organic liquids. However, inorganic compounds are usually not soluble in such liquids, and certainly not in those common in the 1930s. Mann realized that forming complexes of inorganic compounds with agents such as tertiary phosphines, many of which are rather vile smelling and reactive materials, would produce adducts that were soluble in organic liquids. Chatt did his PhD research work on phosphine complexes of palladium, among other related species, and this led to his lifelong interest in basic transition-metal chemistry, transition-metal organometallic chemistry, and the nature of the coordinate bond.

This last subject requires a little explanation. The interest that Mann had in the parachor has long been superseded. However, a coordinate bond between a metal ion acceptor and a donor such as ammonia has been recognized for several decades to be the result of the sharing between the donor and acceptor of a pair of electrons (a lone pair). The extent to which this donation of negatively charged electrons leaves a positive charge on the donor and produces a negative charge on the acceptor has been the subject of research for perhaps sixty years, starting with the the effective founder of the field, Alfred Werner. The amount of charge transfer varies considerably with both the kind of donor and the kind of acceptor. Chatt was one of the first to concern himself experimentally with this problem, using the kinds of compound he had first studied with Mann, and to solve it he employed the most recent advances in preparative inorganic chemistry and in various branches of spectroscopy. His work paralleled that of Dwyer and especially Nyholm, who became a close friend when the latter moved to University College, London. Wilkinson also worked, in part, in related areas, and so did Pearson and Basolo.

Inorganic Chemistry at ICI . Chatt’s brief stay at Imperial College had been very frustrating. The aftermath of the war, with its shortages both of money and of materials, prevented him from doing any significant work. However, his enthusiasm was noted by the then chairman of ICI, Wallace Akers, who was a keen supporter of academic research, and who was also convinced that the company would benefit from having a general group of first-class academic researchers working in new areas in the company’s own laboratories. He persuaded the company to establish such a laboratory, in some temporary buildings on the grounds of a country house called The Frythe, near Welwyn, Hertfordshire, some twenty miles north of London. ICI recruited Chatt directly form his fellowship at Imperial College, and gave him the objective of setting up an academic-style inorganic chemistry laboratory. The name, The Frythe, became synonymous with innovative inorganic chemistry research of the highest order. Although Chatt initially headed a department of one, namely, himself, he built up a famed research group, two of the most eminent members of which, among several others, were Luigi M. Venanzi and Bernard L. Shaw. At The Frythe, Chatt was able to work and publish uninterruptedly on his own projects. He was able to apply his meticulous methodology and integrity to completely novel projects. That ICI did not take commercial advantage of what he produced, though others in other countries did, was a great pity for the company.

During World War II, Chatt had become interested in the peculiar addition compounds that seemed to form between elements such as platinum, on the one hand, and olefins and acetylenes, on the other, organic compounds that contain multiple carbon-carbon bonds but no lone pairs of electrons of the kind recognized in ammonia. The study of these addition compounds gave rise to a series of papers titled “The Nature of the Coordinate Link,” published between 1950 and 1984. Just how an olefin could bind to a transition metal ion when it had no lone pairs, and what the structure of such a complex might be, was very much of a mystery. The ideas generated in these papers remain into the early 2000s a fundamental part of the inorganic chemists’ theoretical armory. It was inferred by Chatt, as described in “Olefin Coordination Compounds,” Parts I (1949) and III (1953), that the electrons forming the carbon-carbon multiple bond could act as lone pairs, and that the negative charge transferred from the olefin to the metal in this process could be partly neutralized by the transfer of other electrons on the metal ion back to the olefin (back-bonding). Such a coordinate bond thus has two parts, formed by transfer of electrons in opposite directions. Not only that, but donors such as the tertiary phosphines, to which Mann had introduced him, were shown to be able to bond to metal ions in a comparable way. There has been some disagreement as to who first publicized this idea of simultaneous transfer of electrons in both directions when forming a coordinate bond, particularly when olefins and acetylenes are involved, and people such as Linus Pauling and Michael J. S. Dewar were important contributors. There is, however, no doubt that Chatt was instrumental in developing it and showing its wide applicability.

The consequences of this work were very wide-reaching. Chatt was one of the first to use infrared spectroscopy to characterize inorganic chemical compounds and to use the frequencies of given infrared absorptions to infer the nature of the bonds producing such absorptions. This later became common, but at that time there were few, if any, commercial infrared instruments available. The ICI workshops constructed one specifically for the use of Chatt’s group, which also did extensive work on the dipole moments of complexes in order to infer charge distributions. This latter technique, the measurement of dipole moments, is no longer widely employed.

Many new complexes, often phosphine complexes, were produced at The Frythe. Together with Sten Ahrland, who came from the Scandinavian school of chemistry that had developed very advanced techniques for measuring stability constants, he employed the Scandinavian methods to compare the intensities of the interactions between various donors (such as ammonia, phosphines, and the related arsines) and various metal-ion acceptors (both transition-metal and non-transition-metal ions) when forming metal complexes. From this work came the generalization that acceptors in these complexes fall into two groups, those designated Class A, which seem to comprise those that do not partake of significant back-bonding, magnesium being a typical example, and those designated Class B, which do. Typical examples of the latter are the platinum group metals. These ideas were later extended and generalized by Ralph G. Pearson to produce the concepts of hard and soft Lewis acids and Lewis bases, which still form a useful part of the inorganic chemist’s theoretical armory.

This was not the end of The Frythe’s influence. Together with Pearson and novices Bernard L. Shaw and Harry B. Gray, both now internationally recognized, Chatt was a participant in one of the first major studies of the mechanism of substitution of groups in inorganic complexes. Such studies were common in organic chemistry, stimulated by the work of researchers such as Ingold, and the results were well understood in electronic terms, comparable studies on inorganic compounds could not be made until the development of novel complexes such as those studied at The Frythe. In the early 2000s, such work is common, but then it was groundbreaking.

There was at least one further development that can be traced back to The Frythe. Chatt reasoned that developing a metal-carbon bond in complexes of donors such as his favorite phosphines with metal ions, for example those of platinum and palladium, could strengthen the supposedly very weak metal-carbon bond. This did indeed turn out to be the case, and the result was a series of elegant and original papers titled “Alkyls and Aryls of the Transition Metals” (1959–1966). This work finally exploded the idea that transition-metal bonds to carbon in, say, alkyl compounds, are inherently very weak, and led to a veritable explosion in preparative chemistry, both inorganic and organic, that changed ideas about transition-metal compounds and had a profound influence on industrial chemistry and catalysis. Almost as a by-product, the first hydride complex (a complex containing a bond between a transition-metal ion and a hydrogen atom) containing no moieties with metal-carbon bonds was characterized at The Frythe. Metal carbonyl hydrides had been recognized for more than fifty years. Many other classes of hydride complex were later known.

This work not only was a fundamental part of the renaissance of inorganic chemistry in the 1950s and 1960s, but it changed completely the prevailing ideas about inorganic compounds and their structures, about transition-metal catalysis, and even about significant aspects of organic synthesis. Nevertheless, in 1962, perhaps because of a less favorable economic climate and with a more focused management, ICI decided to reorganize its research activities, and the decision was made to close The Frythe laboratory and draft Chatt back to northern England to involve him in industrial organic chemicals. This he declined to accept, and when the laboratory was closed, he looked for other employment.

Nitrogen Fixation Research . By this time Chatt already had an international reputation and, in 1961, had been elected to the Royal Society. It was rumored that he would move to the United States, but the then-secretary of the Agricultural Research Council, Sir E. Gordon Cox, persuaded the council to set up a research laboratory for him, to absorb the little biological nitrogen fixation work the council was already funding, and to launch a full-scale effort in both biology and chemistry to uncover the mechanism of biological nitrogen fixation. The conversion of atmospheric nitrogen (or dinitrogen, N2), a very unreactive compound that comprises about 80 percent of atmospheric air, to ammonia (NH3) is achieved industrially using catalysts and elevated temperatures and pressures, but microorganisms can achieve such a conversion in the soil under ambient conditions. Exactly how they do so was then (and remained into the early 2000s) an unsolved problem.

The laboratory, internationally known as the Unit of Nitrogen Fixation, became the leading one of its kind in the world. Initially situated at Queen Mary College in London, that site was ultimately determined to be unsuitable, and in 1964, the unit moved to the University of Sussex in Brighton, East Sussex, with the encouragement of the head of the School of Chemistry and Molecular Science, Colin Eaborn. There the unit was set up in two separate but closely connected sections, the chemistry led by Chatt and the biology led by John R. Postgate, with Chatt as overall director. Eventually, at its zenith in the 1980s, the unit comprised some sixty persons and was notable for its breadth of expertise, ranging from inorganic chemistry at one extreme through biochemistry and microbiology to molecular biology at the other. After a considerable amount of encouragement from Chatt and Postgate, all the various researchers in the unit developed the ability to discuss meaningfully most aspects of the nitrogen fixation problem, whatever their basic discipline, and this unique property attracted a constant stream of researchers from all over the world. The Agricultural Research Council ran the unit on a very loose rein, something that was exceptional by the 1990s, and remained so as of 2006. Nevertheless, this approach was rewarded with a stream of fundamental discoveries that have had an enormous impact on our understanding of both the chemistry and biology of nitrogen fixation. Despite the successes achieved, the successor to the council eventually decided that the direct economic payback for all this academic work was too little, and the unit was allowed to fade away after 1996, when many of its staff were transferred to the John Innes Centre at Norwich. However, what Chatt achieved in chemistry and Postgate in biology is still widely appreciated and used.

Perhaps the most important biological discovery was the ability to transfer a plasmid containing the genes necessary to fix nitrogen from Klebsiella pneumoniae to Escherichia coli. Although this work was within Postgate’s section, Chatt was skilled enough subsequently to present to the council a case for expanding the unit’s genetics effort by about 50 percent. He was successful, and this discovery was the basis for advances in the understanding of the function, genetics, and regulation of biological nitrogen fixation and similar properties of other processes in a large variety of organisms.

The chemistry work, led by Chatt, was at least as influential. It had been believed for some years prior to the 1960s that the enzyme responsible for the biological conversion of dinitrogen to ammonia was a metalloenzyme, possibly containing iron and (or) molybdenum. However, no one had detected any sign of the direct interaction of dinitrogen with a metal compound that might be regarded as a model for the metalloenzyme function. In 1965, Albert D. Allen and Caesar V. Senoff announced the first dinitrogen complex, based upon ruthenium, and containing the moiety Ru—N≡N. Cobalt and iridium dinitrogen complexes appeared soon after. The conversion of the bound dinitrogen to ammonia turned out to be much more difficult and was not achieved until later.

The unit’s chemistry work started in 1965 and took off when the unit moved into its own building in 1969. In that year, in a paper titled “A Series of Nitrogen Complexes of Rhenium(I),” Chatt and his collaborators described the first two extensive series of dinitrogen complexes, based upon rhenium and osmium, both also containing the customary phosphine donors. They also described related nitride complexes, which contain a single nitrogen atom combined with a metal ion.

These dinitrogen complexes proved rather recalcitrant as far as making the dinitrogen react. However, the Chatt group adduced evidence to show that the complexed dinitrogen was probably polarized so that the external nitrogen atom carried a negative charge, a consequence of the two-way flow of electrons between a donor and an acceptor of the kind discussed above. This was surely a way to render the dinitrogen more reactive, and in 1972, the group reported the first reaction of a well-defined dinitrogen complex, of tungsten, a congener of the biological metal molybdenum, to produce a well-defined complex product containing a new nitrogen-carbon bond. The mechanism of this reaction was described subsequently in detail by the Chatt group in “The Mechanism of Alkylation of Dinitrogen Coordinated to Molybdenum(0) and Tungsten(0).” This study remained the major kinetic investigation of a reaction of this kind into the twenty-first century. It led to the establishment of a cyclic system for making amines directly from dinitrogen. In 1972, the controlled protonation of coordinated dinitrogen was achieved, and the protonation all the way to ammonia was reported in 1975. These and many related studies were the basis for what was later described as the Chatt cycle to explain the protonation of dinitrogen, both in these complexes of molybdenum and also in nitrogenase enzymes. As of 2007, it remained an open question whether extension to the nitrogenase enzymes is justified or not.

Later Life and Honors . Chatt retired from the Unit of Nitrogen Fixation in 1978 and gradually withdrew from professional activities. His work was regularly quoted in the literature, and much of it remained current. He was active outside his immediate area of employment all his professional life. For example, he was secretary of the Chemical Society (later the Royal Society of Chemistry) and for over twenty years a member of IUPAC, during which time (1959–1963) he occupied effectively the chair of the Commission on the Nomenclature of Inorganic Chemistry. He was honored by election to several academies, including the New York Academy of Sciences (1978), the American Academy of Arts and Sciences (1985), and the Indian Chemical Society (1984). He received several medals and lectureships, including the American Chemical Society Award for Distinguished Service in the Advancement of Inorganic Chemistry in 1971 and the Wolf Prize for Chemistry in 1981. Her Majesty the Queen appointed him to the rank of Commander of the British Empire (CBE) in 1978.

The Royal Society of Chemistry endowed a lectureship in his name. By its terms, every second year a distinguished chemist, without regard to nationality, is invited to deliver the lecture at several venues within the United Kingdom.

BIBLIOGRAPHY

Documents relating to Chatt’s professional career are deposited at the John Innes Centre, Colney Lane, Norwich, NR4 7UH. A complete bibliography is obtainable from the library of the Royal Society, London; see Eaborn, C., and G. J. Leigh, cited below.

WORKS BY CHATT

“Olefin Coordination Compounds. Part I, Discussion of Proposed Structures: The System Ethylene-Trimethylborine.” Journal of the Chemical Society(1949): 3340–3348.

“The Nature of the Co-ordinate Link. Part I, Halogen-Bridged, Binuclear Platinous Complexes.” Journal of the Chemical Society (1950): 2301–2310.

“The General Chemistry of Olefin Complexes with Metallic Salts.” In Cationic Polymerization and Related Complexes, edited by P. H. Plesch. Cambridge, U.K.: Heffer, 1953.

With L. A. Duncanson. “Olefin Coordination Compounds. Part III, Infra-red Spectra and Structure of Acetylene Complexes: Attempted Preparation of Acetylene Complexes.” Journal of the Chemical Society (1953): 2939–2947.

With L. A. Ducanson and B. L. Shaw. “A Volatile Chlorohydride of Platinum.” Proceedings of the Chemical Society (1957): 343.

With S. Ahrland, N. R. Davies, and A. A. Williams. “The Relative Affinities of Coordinating Atoms for Silver Ions. Part I, Oxygen, Sulphur, and Selenium.” Journal of the Chemical Society (1958) 264–276.

With S. Ahrland, N. R. Davies, and A. A. Williams. “The Relative Affinities of Coordinating Atoms for Silver Ions. Part II, Nitrogen, Phosphorus, and Arsenic.” Journal of the Chemical Society (1958): 276–288.

With B. L. Shaw. “Alkyls and Aryls of the Transition Metals. Part I, Complex Methylplatinum(II) Derivatives.” Journal of the Chemical Society (1959): 705–716.

With F. Basolo, H. B. Gray, R. G. Pearson et al. “Kinetics of the Reaction of Alkyl and Aryl Compounds of the Nickel Group with Pyridine.” Journal of the Chemical Society (1961): 2207–2215.

With J. M. Davidson. “The Tautomerism of Arene and Ditertiary Phosphine Complexes of Ruthenium(0), and the Preparation of New Types of Hydridocomplexes of Ruthenium (II).” Journal of the Chemical Society (1965): 843–855.

With J. R. Dilworth and G. J. Leigh. “A Series of Nitrogen Complexes of Rhenium(I).” Chemical Communications(1969): 687–688.

With G. A. Heath and G. J. Leigh. “The Formation of a Nitrogen to Carbon Bond in a Reaction of a Dinitrogen Complex.” Journal of the Chemical Society, Chemical Communications (1972): 444–445.

With A. J. Pearman and R. L. Richards. “The Reduction of Mono-coordinated Molecular Nitrogen to Ammonia in a Protic Environment.” Nature 253 (1975): 39–40.

With R. A. Head, G. J. Leigh, and C. J. Pickett. “The Mechanism of Alkylation of Dinitrogen Coordinated to Molybdenum(0) and Tungsten(0).” Journal of the Chemical Society, Chemical Communications (1977): 299–300.

With P. B. Hitchcock, A. Pidcock, C. P. Warren et al. “The Nature of the Coordinate Link. Part XI, Synthesis and phosphorus-31 nuclear magnetic resonance spectroscopy of platinum and palladium complexes containing side-bonded (E)-diphenyldiphosphene. X-Ray crystal and molecular structures of [Pd{(E)-PhP=PPh}(Ph2 PCH2 CH2 PPh2 )] and [Pd{[(E)-PhP=PPh][W(CO)5 ]2 }(Ph2 PCH2 CH2 PPh2 )].”Journal of the Chemical Societ, Dalton Transactions (1984) 2237–2244. This was the last paper in the series, “The Nature of the Coordinate Link.”

OTHER SOURCES

Brock, William H. The Fontana History of Chemistry. London: Fontana Press, 1992. See especially pp. 591–618.

Dixon, R. A., and J. R. Postgate. “Transfer of Nitrogen Fixation Genes by Conjugation in Klebsiella Pneumoniae.” Nature(London) 234 (1971): 47–48.

Eaborn, C., and G. J. Leigh. “Joseph Chatt, C.B.E ., 6 November 1914–19 May 1994.” Bibliographic Memoirs of Fellows of the Royal Society 42 (1996): 96–110.

Hussain, W., G. J. Leigh, and C. J. Pickett. “Stepwise Conversion of Dinitrogen Coordinated to Molybdenum into an Amine and an Imido-complex: Relevance to the Reactions of Nitrogenase.” Journal of the Chemical Society, Chemical Communications (1982): 747–748.

Leigh, G. J. “A Celebration of Inorganic Lives. Interview of Joseph Chatt.”Coordination Chemistry Reviews 108 (1991): 1–25

——. “Professor Joseph Chatt CBE FRS.”Coordination Chemistry Reviews 154 (1996): 1–3

——. In Nitrogen Fixation at the Millennium, edited by G. J. Leigh: Elsevier, Amsterdam, Netherlands; Boston, 2002, Chapter 11, Dinitrogen Chemistry.

——. J. N. Murrell, W. Bremser, and W. G. Proctor. “On the State of Dinitrogen Bound to Rhenium.” Chemical Communications (1970): 1661.

——. and N. Winterton, eds. Modern Coordination Chemistry: The Legacy of Joseph Chatt. Cambridge, U.K.: Royal Society of Chemistry, 2002.

G. Jeffrey Leigh

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