The author gives this chapter the same title as Ronald Nyholm's 1956 book, The Renaissance of Inorganic Chemistry, in which he defines inorganic chemistry as “the integrated study of the formation, composition, structure, and reaction of the chemical elements and their compounds, excepting most of those carbon”.
The author begins this detailed account of renewed vigor in inorganic chemistry research with a detailed summary of Alfred Werner's extensive development of coordination chemistry in the section titled "Werner’s New Ideas". Alfred Werner, whose name is considered synonymous with coordination chemistry, did his first studies on stereoisomerism. Frankland and Kekule’s theory of valency provided an explanation for the structures of carbon compounds and simpler inorganic compounds but there was still debate on whether elements have fixed valencies. This was to loom largely in Werner's analysis of structure and bonding in coordination complexes. The author summarizes Werner's work on coordination chemistry with the following three comments:
1) Werner’s coordination of water directly to the metal “not only solved the problem of water of crystallization, but formed a bridge between the hydrate theories of Mendeleev and others and the new dissociation theory of Arrhenius. Conductivity and dissociation were dependent on the nature of solvents because only those solvents which can combine with metal salts to form coordination radicals are able to allow electrolytic conduction”. [I think what this means is that conductivity, which, itself, is dependent on the extent of dissociation, depends on the solvent because dissociation can only occur if solvent molecules are able to coordinate with the metal cation.]
2) It stimulated thinking on the spatial representation of complexes that have 6 or 4 particles surrounding the metal cation and consideration of stereochemistry (e.g. geometric isomerism) by inorganic chemists. An insightful finding cited was the observation that because the platinum compound Pt(NH3)2Cl2 has no optical activity, it must have a square planar arrangement with two geometric isomers as is now taught.
3) Werner’s ideas on coordination complexes ‘demanded’ a “revolution in valence theory” for “how could a divalent copper atom bond six ammonia radicals to itself”? In answer to this type of question, Werner mused, “It would also appear that the amount of residual charge – of surplus affinity – possessed by a radical after combination with others depends both on its own nature and that of the radical or radicals with which it becomes associated”. “It was, he suggested, as o the metal were a positive sphere surrounded by a neutral shell of water or ammonia whose inner surface was rendered negative, and consequently, its outer surface positive.” Werner further distinguished the valency of an atom from its “coordination number”: the coordination number refers to the number of groups combining with a metal to form a complex and the valency the number of monovalent atoms that can bound directly to the atom.
Along with Werner's foundational discoveries and theories at the end of the 19th century, Nyholm and other coordination chemists attribute the renewed interest and research in inorganic chemistry to Sidgqwick's work and 'interpretation of coordination chemistry' in the 1920's. In 1927, Nevil Vincent Sidgwick published “an influential reworking of Werner’s theory in terms of Bohr’s theory of spectra and atomic constitution and Lewis’ view on valency and chemical combination”. In this text, he indentified three different ways that atoms of the elements link together in compounds and complexes: polar or ionizable bonds between oppositely charged ions; nonpolar, covalent, shared electron pair of Lewis and Langmuir, and coordinate linkages of Werner which he also recognized as covalent, using the term ‘covalent link’ for the case in which a ligand donates a shared electron pair to the metal acceptor atom and defining the coordination number as the number of shared electron pairs donated. In reconciling Werner’s coordination theory with traditional structural theory, Sidgwick pointed to Pauling’s statement that “most coordination compounds were resonance hybrids” (like sulfuric and nitric acid are) pointed to a solution involving a more complete theory on valency that recognizes a third type of linkage “a covalency in which both electrons are supplied by the same atom". Mathematical analysis ultimately led to the determination of a ‘crystal-field stabilization energy’ arising from filling in d-orbitals with relatively lowered energy due to decreased electrostatic repulsion from the incoming ligand [the term crystal pertains to the first use of the analysis in crystallography]. Further analysis using both crystal theory and molecular orbital theory eventually led to the formulation of the ligand field theory now taught in General College Chemistry.
The author included sections on Australian and Japanese Chemistry pointing out that in both these countries, although culturally dissimilar, chemistry started out with a more utilitarian focus. The disciplines of chemistry and physics were institutionalized in both countries in the 1870’s. Many of the early pioneers were educated in Europe and, in Australia in addition, some were British.
In 1918, the Australian Chemical Institute was founded but due to long distances, there was not much interaction between the regional chapters. Even as more chemistry research departments started to be developed, most of the senior posts went to British Chemists. The development of chemistry was further slowed by the difficulty of receiving communications from Europe. By 1975, however, the first Australian chemist won the Nobel Prize for his work on the stereochemistry of enzyme-catalyzed reactions.
In Japan, between 1888 and 1930, doctorates in engineering and medicine outnumbered those in chemistry for which only 25% had a basic research focus. The lack of a Japanese chemical vocabulary made lecturing in Japanese difficult. Bureaucracy made it challenging for Japanese chemists showing academic promise to pursue further training and a pedagogical tradition of teaching as information transfer did not encourage innovation. Furthermore, “a cultural hierarchical fear of challenging an older peer or teacher also inhibited criticism and novelty and discouraged cooperate research”. While the Tokyo Chemical Society was founded in 1878 by foreign teachers followed by a journal publication starting in 1880, it was not until 1972 that an English-language journal was first published. The author featured some early leaders in Japanese chemistry who were educated in Europe. One of these was Ikeda Kibunae known for his discovery and patenting in 1908 of a method of producing monosodium glutamate from kelp which became the basis for Japan’s first major chemical industry. Demand for trained engineers, managers, and skilled factory workers led to the expansion of the university system in the 1920’s (like in America and Australia). Interest in fuels chemistry during the Second World War led to quantum mechanical studies of unsaturated hydrocarbons. In 1950, Kenichi Fukui developed the frontier orbital theory of reactions that states that “the progress of reactions depends upon the geometry and relative energies of the highest recipient molecular orbital of one reactant and the lowest molecular orbital of the other”. In 1981, Fukui and Roald Hoffman won the Nobel Prize for this work.
Coordination chemistry was particularly highlighted by the author in the further development of chemistry in Australia. Eustace Turner’s work (he was British) and collaboration with an Australian colleague on the characterization of an arsenic coordination compound in 1921 put “Australian chemistry firmly on the world map of chemistry” and had been the ‘catalyst for Australia’s future reputation in coordination chemistry”. [They also prepared an arsenic analogue of indole which they were going to call “arsole” which did not escape the censorious eye of the editor and was then changed to arsindole] Burrows, with his students, further worked on synthesizing arsenic complexes of zinc, cadmium, mercury, and platinum. David Mellor of Tasmania used x-ray crystallography to study structure of coordination compounds, including the coordination chemistry of palladium, and showed “how the magnetic properties of transition metals could be used to clarify their complicated stereochemistry”.
The author devotes the last section of the chapter on Nyholm’s Renaissance, owing to Nyholm's contribution to coordination chemistry. Ronald Nyholm, was born in Broken Hill, Australia, a mining town whose streets were given chemical names, completed his Ph.D. with Ingold as supervisor. He worked with Dwyer (Sydney Technical College)and published papers on the complexes of Rhodium. Nyholm’s work showed that certain ligands can induce what historically has been thought of unusual valency states (e.g. nckel(IV)) determined from measurements of magnetic moments. He was also able to induce higher coordination numbers (e.g. Mo(VII) and Ti(VIII)) using unusual ligands. Working with Gillespie, they were able to rationalize the small deviations from predicted bonding angles in regular geometries (linear, trigonal, tetrahedron, etc.) by pointing out that electrons with similar spins are repelled more than those with opposite spins and that bonding pair-bonding pair repulsion is weaker than bonding pair-lone pair repulsion. Becuase of his organization skills, Nyholm was able to make predictive use of patterns, anomalies, and gaps he discovered within the transition metal groups by “comparing, contrasting, and correlating the properties of transition metal complexes horizontally and vertically within their periodic table positions”. An example of this is the deduction and later experimental preparation of transition metals that can form metal-metal bonding. As the author outs it, “Like Ingold for organic chemistry, Nyholm perceived that inorganic chemistry would benefit from the use of large-scale instrumentation for mass spectrometry and spectrophotometry. Indeed, it was Nyholm’s contention that ‘the impact of quantum mechanics and of modern physical methods of attack are the main reasons for the renaissance of inorganic chemistry, leading to the present period of rapid growth”. In the realm of chemical education, Nyholm advocated for an undergraduate teaching curriculum that involves the integrated use of tools of chemical investigations: “I believe that we should find more time to enable students to acquire these techniques of inorganic chemistry, as for instance, the handling of substances in the absence of air or moisture, the manipulation of gaseous substances, and reactions involving low or high temperatures. Finally, I am convinced that, in keeping with the new sense of purpose in inorganic chemistry, the maximum opportunity should be provided for the undergraduate to prepare a compound, to establish its purity by analysis, and to investigate as many of its properties by chemical and physical techniques as he [sic] is able to do. This means that we effectively illustrate the wholeness of modern chemistry, and I believe that we thereby develop a genuine enthusiasm for this subject at undergraduate level.” In 1963, Nyholm encouraged further progress in chemistry teaching and research by recognizing that “chemistry’s boundaries were dissolving and overlapping with interesting areas of physics, biology, geology, and mathematics”. He recognized the necessity of sharing expensive instrumentation and that undergraduates should be able to use them too.
Author's chapter conclusion in his own words on the Renaissance of Inorganic Chemistry: “The central place of inorganic chemistry is now unquestionable. The synthesis of extraordinary structures and insights into unexpected mechanisms continues. organometallic chemistry was, for example, transformed with the synthesis of the first sandwich compound, ferrocene, in 1957. The power of transition complexes, especially those of platinum, to catalyse important polymerization reactions has similarly transformed industrial chemistry since 1950. Far from being outplayed, inorganic chemistry in the second half of the twentieth century has proved an essential component of the understanding of biochemistry, analytical chemistry, catalysis, electrochemistry, mineralogy, crystallography, radiochemistry and in all industrial processes involving high temperatures, catalysis and semiconductors.”
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