Modern Inorganic Synthetic Chemistry

Ruren Xu, Yan Xu, Ruren Xu, Yan Xu

• Publisher: Elsevier
• Year: 2010
• ISBN:
  9780444536006
• Topic: Ciencias físicas
• Subtopic: Química inorgánica

The book has four main parts. Inthe first partthe discussion centers on inorganic synthesis reactions, dealing with inorganic synthesis and preparative chemistry under specific conditions: high temperature, low temperature and cryogenic, hydrothermal and solvothermal, high pressure and super-high pressure, photochemical, microwave irradiation and plasma conditions. The second part systematically describes the synthesis, preparation and assembly ofsix important categories of compounds with wide coverage of distinct synthetic chemistry systems: coordination compounds, coordination polymers, clusters, organometallic compounds, non-stoichiometric compounds and inorganic polymers. In the third part seven important representative inorganic materials are selected for discussion of their preparation and assembly, including porous, advanced ceramic, amorphous- and nano-materials, inorganic membranes, synthetic crystals and advanced functional materials. The last part of the book, which is also its distinct feature, addresses the frontiers of inorganic synthesis and preparative chemistry. These finaltwo chapters introduce the two emerging synthetic areas. Included are approximately 3000 references, a large proportion of which are from the recent decade.

• Focuses on the "chemistry" of inorganic synthesis, preparation and assembly of various compounds and describes all inorganic synthesis methods
• New state of the art inorganic synthesis chemistry areas
• Inclusion of a number of real examples for the preparation and assembly of important classes of materials
• More than 3, 000 reference to the primary literature
• Comprehensive state of the art reviews written by the experts in the area

Chapter 1 Introduction - Frontiers in Modern Inorganic Synthetic Chemistry

Ruren Xu, Jilin University, China

Synthetic chemistry is at the core of modern chemistry; it provides the most powerful means for chemists to create the material foundation for our envisioned world. Its main objective is to create a large variety of compounds, phases, materials, and ordered chemical systems needed by our rapidly advancing society, going considerably beyond just finding and synthesizing naturally existing compounds. According to recently published studies, over 50 million compounds, naturally existing or not, have been discovered or synthesized, some of which have become indispensable to our daily life. These compounds have provided the basis for many scientific and technological advances in the recent history. In turn, these advances have created rapidly increasing needs for new materials with specific structures and functions, posing challenges to, as well as creating opportunities for synthetic chemists. Specifically, we see increasing needs in this new century, for novel synthesis strategies and techniques, as well as for the related scientific understanding, gearing toward green synthesis, biomimetic synthesis, inorganic synthesis under extreme conditions, and molecular and tectonic engineering of inorganic materials, in efficient, rationally designed and economic manners. We believe that these are among the most essential key elements for the continuing and rapid advancement of science and technology in this new century [1,2].

In the past century, advances in synthetic chemistry have often been the key driving force for the industrial revolutions and birth of new science and technologies; examples of this sort have been numerous [2]. For instance, F. Haber, in the early twentieth century, invented a high-pressure technique to synthesize ammonia, the key ingredient of chemical fertilizers, from the abundantly available H₂ and N₂ using osmium as the catalyst. Twenty years later, C. Bosch improved the technique by using inexpensive iron instead of expensive osmium as the catalyst, which laid a solid foundation for the human society to maintain a continued increase in food production to keep up with the human population increase; a major challenge that we have been facing since the past century. Because of their profound contributions to science as well as to the human society, Haber and Bosch received Nobel prizes in chemistry in 1918 and 1931, respectively. Health industry is another area where synthetic chemistry has been playing pivotal roles. Outstanding examples since the mid-twentieth century include the successful syntheses of SAS drug, penicillin, a variety of antibiotics and other medicines, which have substantially improved and continue to improve our overall abilities in treating human diseases and fighting against them. Our ability in producing the three major classes of synthetic materials, namely synthetic fiber, synthetic plastic, and synthetic rubber, has paved the way for many of the recent industrial and agricultural advances. There is no doubt that chemistry, especially synthetic chemistry, has been making considerable contributions to improve the living conditions of the human society.

From a scientific perspective, a pool of very large number of new materials created by synthetic chemistry has provided plenty of samples for studying the structure–function (property) relationships of materials as well as their syntheses, facilitating scientists to study the fundamental chemistry of these materials, which has become a driving force in the recent developments of chemistry and related sciences. For example, the successful preparation of single crystalline silicon and numerous semiconductive materials has fueled the emergence of information technology; the production and posttreatment of nuclear fuel of uranium and plutonium, the key to the nuclear technology and safe application, have all been built on chemical technologies with roots in synthetic chemistry. Similar can be said about other high technologies such as laser, nanotech, aviation, and space technology. Without a doubt, the so-called six great technology inventions in the twentieth century would have never materialized without the foundational work by generations of synthetic chemists in the past. The same is true about other technological breakthroughs and growth points in related sciences such as semiconductor, super conduction, cluster, and nanotechnology.

Modern inorganic synthetic chemistry, an important branch of synthetic chemistry, has evolved considerably from the traditional synthesis and preparation of inorganic compounds, which now includes the synthesis, assembly, and preparation of supramolecular and high-level ordered structures in its studies. In recent years, we have been witnessing that an increasingly large number of new inorganic compounds, phases, and complex materials are being synthesized and assembled, having made inorganic synthetic chemistry a key driver for many new scientific and technological developments and advancements. We anticipate that inorganic synthetic chemistry will continue to play equally or more important roles in science as well as in our upcoming life.

1.1 DEVELOPMENT OF NEW SYNTHETIC REACTIONS, SYNTHETIC ROUTES, TECHNOLOGIES AND ASSOCIATED BASIC SCIENTIFIC STUDIES

1.1.1 The Basic Inorganic Compounds

This basic class includes covalently bonded molecular compounds, coordination compounds, cluster compounds, metal organic compounds, nonstoichiometric compounds and inorganic polymer, among others.

1.1.2 Inorganics and Materials with Specific Structures

Study of inorganic compounds and phases with specific structures is becoming increasingly important as the need for materials with specific properties and functions continues to rise. It is well accepted that the properties and functions of materials are determined by their structures and compositions. More specifically, such properties and functions are often determined by the characteristics of high-level molecular structures such as those of molecular aggregates, ordered molecular assemblies, and structures in condensed states instead of single molecular structures. Take defects for example, the properties and functions of materials often result from various forms of structural defects in their component compounds or phases in condensed state. A key reason that many complex oxides are being used as popular substrates for functional materials is that they can form many types of structural defects in addition to their many adjustable component elements. Hence, it has become a major topic at the forefront of inorganic chemistry research to study the preparation of solid-state matters with specific structural defects and the associated principles as well as related detection techniques. In addition, the key research topics in today’s inorganic chemistry also include preparation of surfaces and interfaces with specific structures and properties, stacking of layered compounds, preparation of specific polytypes and their intergrowths as well as intercalation structures and low-dimensional structures of inorganic compounds, synthesis and preparation of inorganic compounds with mixed valence complexes and clustered compounds with specific structures, as well as the rapidly emerging and increasingly useful porous compounds with specific channel structures such as microporous crystals, meso- and hierarchical porous materials. Also particularly interesting is the preparation of phases that tend to form distinct structures and are able to form large varieties of distinct structures under extreme synthetic conditions like high or ultrahigh pressures. While a few synthesis examples with the aforementioned characteristics have been reported in the literature, such studies have generally been done in rather ad hoc manners, often accomplished through utilizing the particularity of specific reactions or specific synthesis techniques rather than based on new understanding of a general class of synthesis problems and new synthesis technologies. The latter is clearly more important for the future development of synthetic chemistry.

1.1.3 Inorganics and Materials in Special Aggregate States

Another important class of materials are the compounds in special aggregate state, such as in nano state, ultrafine particles, clusters, noncrystalline state, glass state, ceramic, single crystal, and other matters with varying crystalline morphologies such as whisker and fiber. The rapid emergence of nanoscience and technology strongly suggests that different aggregate states of the same matter could exhibit different properties and have different functions. The understanding of this could have substantial implications to the future development of science as well as new functional materials.

1.1.4 Assembly of High-level Ordered Structures

There is an emerging class of functional inorganic materials, commonly characterized as being highly ordered supramolecular systems, formed via self-assembly among molecules or molecular aggregates through molecular recognition. The key interaction forces in the formation of such large molecular assemblies are intermolecular non- or weak-bond interactions (van der Waals and hydrogen bond). Examples of such materials include coordination polymers, inorganic polymers, and molecular systems with specific structural features such as nanosystems, capsula, ultrathin membrane (monolayer membrane, multilayer composited membrane), interfaces, two-dimensional layered structures, and three-dimensional biological systems; many of which have been widely used for fabricating high-tech microdevices. Self-assembly is increasingly becoming a key and practical technique in the synthesis and preparation of complex functional systems. It has even been suggested that the introduction of self-assembly-based synthesis techniques could fundamentally advance the chemical production processes that are being widely used in the current industries [2].

1.1.5 Composition, Assembly, and Hybridization of Inorganic Functional Materials

The following areas have received considerable attention in recent years: (1) multi-phase composition of materials including enhanced or reinforced fiber- (or whisker-)based materials, the second-phase particle dispersion materials, two- or multi-phase composite materials, inorganic and organic materials, inorganics and metals, and functional gradient materials as well as nanomaterials; and (2) composite material-related host–guest chemistry, which represents a highly interesting and a very challenging research area. The research focuses include, for example, the assembly of different types of chemical entities in hosts with microporous or mesoporous frameworks such as quantum dot or super lattice-forming semiconductive clusters, nonlinear optical molecules, molecular conductors made of linear conductive polymers and electron transfer chains as well as D–A transfer pairs. All these complex composites could be assembled through synthetic routes consisting of ion exchanges, CVDs, “ships in bottle” and microwave dispersion; (3) nano-hybridization of inorganics and organics, which represents a rapidly emerging interdisciplinary field. It studies the formation of new hybrid materials through combining polymerization and sol–gel processes. These hybrid materials possess those properties which are generally absent in pure inorganics or pure organics, and are increasingly being used in fiber optics, wave propagation, and nonlinear materials. It is worth noting that the first survey about this emerging field was published in 1996 by P. Judeinstein [3].

As outlined above, a key task in today’s inorganic synthetic chemistry is to develop novel synthetic reactions, synthetic routes, and associated techniques aiming to create new functional materials with specifically desired multilevel structures in condensed states. As per the past experience, the discovery of a novel and effective synthetic route or technique has typically led to the creation of a large class of new matters and materials. For example, the advent of sol–gel synthetic route has been a key reason for the development and emergence of nano-states and nanocomposite materials, glass states and glass composites, ceramic and ceramic-based composites, fibers and related composites, inorganic membranes and composite membranes, and hybrid materials. The core chemistry of this synthetic route is hydrolysis and polymerization of starting reactant molecules (or ions) in aqueous solution, i.e., from molecular → polymeric state → sol → gel → crystalline state (or noncrystalline state). This synthetic process could possibly be regulated differently at each individual reaction step so as to create solid-state compounds or materials with different structures or in different aggregate states. While highly promising, we are clearly not there yet due to the complexity as well as our limited understanding of polymerization processes of inorganic molecules in both theoretical and experimental executions. Thus, fundamental studies of these issues represent key areas of focus in today’s inorganic synthetic chemistry.

In summary, the near and intermediate-term objectives for today’s inorganic synthetic chemists are to develop novel and more effective synthetic technologies and to carry out related theoretical studies aiming to gain better understanding of the desired new synthesis capabilities which are both economical and environment-friendly.

1.2 Basic Research in Support of Green Synthesis

The vast majority of known synthetic reactions, especially those used in the preparation of a large variety of rare elements from their ores or raw materials, in the production of fine chemicals as well as in medical and pharmaceutical industries, produce large amounts of by-products, which, along with the used chemicals, solvents, additives, and catalysts, often add major pollutants to our environment and have created considerable environmental issues in the past. Thus, it has become absolutely essential to study ways to considerably lower or completely remove environmental pollution produced by the current chemical industry. While this has posed substantial challenges for synthetic chemists, it has also created new opportunities to further develop synthetic chemistry toward new and healthier directions. Green chemistry, clean technologies, and environment-friendly chemical processes have now become a common conviction of many chemists. Ideal synthesis, a concept proposed by Wender [4] in 1996, aims to “make complex molecules from simple starting materials in a manner that is operationally simple, fast, safe, environmentally acceptable and resource efficacious.” This definition has essentially defined the general direction for realizing green syntheses. In 2009, Noyori [5] proposed that we should aim at synthesizing target compounds with a 100% yield and 100% selectivity and avoid the production of waste. This process must be economical, safe, resource-efficient, energy efficient, and environmentally benign. In this regard, the atom economy and the E-factor should be taken into account. The 3Rs (re...