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Professor Mingos’ research has effectively combined synthetic chemistry, spectroscopic studies, X-ray crystallographic determinations and theoretical approaches to a wide range of important chemical problems. His international reputation is founded primarily on the development of theoretical generalisations which account for the structures of inorganic cluster compounds. In the early 1970s he and Professor Ken Wade of Durham University pioneered the Polyhedral Skeletal Electron Pair Theory which related the structures of cluster compounds to the their total number of valence electrons. This represented a cluster analogue of the Valence Shell Electron Pair Repulsion Theory developed for simple molecular compounds in earlier decades. Nobel Laureate Roald Hoffmann has described these contributions as the most important conceptual development in inorganic chemistry in the 1970s. In the 1980s he successfully extended these generalisations to more complex condensed and high nuclearity clusters. This body of work has been summarised in the book (with D.J. Wales) "Introduction to Cluster Chemistry". These developments and his work on the isolobal analogy with Professor Roald Hoffmann have had an important impact on the way chemists view polyhedral molecules and have profoundly influenced the synthetic goals of many experimental inorganic chemists and opened up an area of chemistry in between the traditional areas of transition metal and main group chemistry. He also extended these theoretical concepts to clusters generated in molecular beam experiments. These ideas have provided a simple account of the geometric preferences of alkali metal, silicon and nickel carbonyl clusters in the gas phase and established important links between this area and the more mature molecular cluster field.
His influence has extended beyond the realm of cluster chemistry. His theoretical papers on fluxional organometallic and cluster molecules, nucleophilic substitution reactions at co-ordinated polyenes (Davies, Green Mingos Rules) and his analysis of the bonding of small molecules co-ordinated to transition metals have had a major and lasting impact. For example, his analysis of the symmetry restrictions associated with the haptotroic rearrangements of metal polyene complexes profoundly influenced the interpretation of the spin saturation nmr experiments of Mann.
He has combined his synthetic and theoretical skills most effectively in the area of gold cluster chemistry He has made and characterised a large number of novel compounds in this area and has used theoretical ideas to give the area an intellectual coherence. In addition he has made a number of notable structural predictions which have subsequently been realised. For example, he predicted the stoichiometry and geometry of the first example of an icosahedral gold cluster compound several years prior to its synthesis and characterization in his laboratories. He also predicted the gold carbido cluster compounds which have been widely studied in recent years by Schmidbaur. Most recently his theoretical analysis on small gold clusters have been shown to be relevant to very large cluster compounds which are important in the development of nanotechnology. In the area of platinum clusters he has utilised a similar combination of skills to generate novel sandwich cluster compounds and many compounds containing both gold and platinum. His group synthesised and determined the structure of a novel and beautiful catenane molecule containing two interlinked 6 atom gold rings.
His combination of experimental and theoretical research is also effectively illustrated by his studies on metallocarborane compounds, which defined the electronic origins of the 'slip' distortions frequently observed in these compounds and laid down the methodology for understanding the conformational preferences of compounds containing angular metal fragments. This type of conformational analysis was subsequently extended to many other organometallic systems by Hoffmann and Albright.
Although much of his theoretical work has been based on semi-empirical molecular orbital calculations he has also made more fundamental contributions to cluster bonding theory. Most notably he has explored the group theoretical implications of Stone's Tensor Surface Harmonic Theory and thereby accounted for many apparent exceptions to the simple electron counting generalisations. He also published general theoretical accounts of the noble gas rule and non-bonding orbitals in molecular systems.
He has made significant contributions to the application of spectroscopic techniques to inorganic molecules. In particular he was the first chemist to use 15N nmr techniques for distinguishing linear and bent nitrosyl complexes and completed an elegant study of their fluxional interconversions using a combination of solution and magic angle solid state nmr techniques. In collaboration with J.C. Green he established for the first time the application of pes studies to metal carbonyl cluster compounds. He has applied other techniques notably electronic spectroscopy, infrared spectroscopy, Mossbauer spectroscopy, and X-ray photoelectron spectroscopy to elucidate structural problems associated with cluster and co-ordination compounds. For example, he provided the first example of skeletal isomerism in cluster chemistry and has defined several unusual co-ordination modes for the sulphur dioxide ligand.
He has pioneered the application of microwave dielectric heating effects for accelerating chemical reactions in solution and the solid state. Not only has he developed new methodologies for undertaking such studies, but he has also demonstrated their applicability to organometallic, co-ordination, solid state and intercalation reactions. This research resulted in a prize from the International Microwave Power Institute for the most outstanding paper in Journal of Microwave Power in 1994 and the Michael Collins Prize for innovation in microwave chemistry in 1996.
In the 1990s he contributed to the field of crystal engineering by designing complexes with complementary hydrogen bonding functionalities which can be put together to form a wide range of interesting solid state structures. This led to some fascinating compounds which resulted in anion recognition and the incorporation of halide anions in complex structures based on co-ordination compounds.
These contributions are discussed more fully in the introduction of a special volume of Inorganica Chimica Acta dedicated to him and written by some of his former students: Inorganica Chimica Acta, volume 359, issue 11, 2006 : ISBN 0020-1693.
In addition to his research contributions Professor Mingos has always shown a great interest in chemical education and communication. He has published many reviews, a monograph on cluster chemistry, undergraduate textbooks and served on the editorial boards of many journals. He acted as Regional Editor of Journal of Organometallic Chemistry from 1996 to 2005 and is Managing Editor of Structure and Bonding since 2000 and co-editor with Robert Crabtree of Comprehensive Organometallic Chemistry.