Inorganic chemistry deals with the synthesis and behavior of inorganic and organometallic compounds. This field covers all chemical compounds except the myriad organic compounds (carbon-based compounds, usually containing C-H bonds), which are the subjects of organic chemistry. Many inorganic compounds are ionic compounds, consisting of cations and anions joined by ionic bonding. Important classes of inorganic compounds are the oxides, the carbonates, the sulfates, and the halides. Many inorganic compounds are characterized by high melting points. Inorganic salts typically are poor conductors in the solid state. When one reactant contains hydrogen atoms, a reaction can take place by exchanging protons in acid-base chemistry. Inorganic compounds are found in nature as minerals. The first important man-made inorganic compound was ammonium nitrate for soil fertilization through the Haber process. Inorganic compounds are synthesized for use as catalysts such as vanadium(V) oxide and titanium(III) chloride, or as reagents in organic chemistry such as lithium aluminium hydride. Subdivisions of inorganic chemistry are organometallic chemistry, cluster chemistry and bioinorganic chemistry. Inorganic chemistry is a highly practical area of science. The manufacturing of fertilizers is another practical application of industrial inorganic chemistry.
Descriptive inorganic chemistry focuses on the classification of compounds based on their properties. When studying inorganic compounds, one often encounters parts of the different classes of inorganic chemistry (an organometallic compound is characterized by its coordination chemistry, and may show interesting solid state properties). Different classifications are:
Classical coordination compounds feature metals bound to "lone pairs" of electrons residing on the main group atoms of ligands such as HO, NH, Cl, and CN. In modern coordination compounds almost all organic and inorganic compounds can be used as ligands. Main group compounds have been known since the beginnings of chemistry, e.g., elemental sulfur and the distillable white phosphorus. Typical main group compounds are SiO, SnCl, and NO. Many main group compounds can also be classed as “organometallic”, as they contain organic groups, e.g., B(CH)). Main group compounds also occur in nature, e.g., phosphate in DNA, and therefore may be classed as bioinorganic. Examples: tetrasulfur tetranitride SN, diborane BH, silicones, buckminsterfullerene C.
Compounds containing metals from group 4 to 11 are considered transition metal compounds. Compounds with a metal from group 3 or 12 are sometimes also incorporated into this group, but also often classified as main group compounds. Transition metal compounds show a rich coordination chemistry, varying from tetrahedral for titanium (e.g., TiCl) to square planar for some nickel complexes to octahedral for coordination complexes of cobalt. A range of transition metals can be found in biologically important compounds, such as iron in hemoglobin.
Examples: The metal (M) in these species can either be a main group element or a transition metal. Operationally, the definition of an organometallic compound is more relaxed to include also highly lipophilic complexes such as metal carbonyls and even metal alkoxides. Examples: Clusters can be found in all classes of chemical compounds. But metal-metal bonded dimetallic complexes are highly relevant to the area. Clusters occur in "pure" inorganic systems, organometallic chemistry, main group chemistry, and bioinorganic chemistry. Medicinal inorganic chemistry includes the study of both non-essential and essential elements with applications to diagnosis and therapies.
Included in solid state chemistry are metals and their alloys or intermetallic derivatives. An alternative perspective on the area of inorganic chemistry begins with the Bohr model of the atom and, using the tools and models of theoretical chemistry and computational chemistry, expands into bonding in simple and then more complex molecules. Precise quantum mechanical descriptions for multielectron species, the province of inorganic chemistry, is difficult. Inorganic chemistry has greatly benefited from qualitative theories. Within main group compounds, VSEPR theory powerfully predicts, or at least rationalizes, the structures of main group compounds, such as an explanation for why NH is pyramidal whereas ClF is T-shaped. A central construct in inorganic chemistry is the theory of molecular symmetry. Mathematical group theory provides the language to describe the shapes of molecules according to their point group symmetry. An alternative quantitative approach to inorganic chemistry focuses on energies of reactions. An important and increasingly popular aspect of inorganic chemistry focuses on reaction pathways. The mechanisms of reactions are discussed differently for different classes of compounds.
The mechanisms of main group compounds of groups 13-18 are usually discussed in the context of organic chemistry (organic compounds are main group compounds, after all). The mechanisms of their reactions differ from organic compounds for this reason. The chemistry of the lanthanides mirrors many aspects of chemistry seen for aluminium.
Mechanisms for the reactions of transition metals are discussed differently from main group compounds. These themes are covered in articles on coordination chemistry and ligand. Traditionally homogeneous catalysis is considered part of organometallic chemistry and heterogeneous catalysis is discussed in the context of surface science, a subfield of solid state chemistry. NMR spectroscopySoluble inorganic compounds are prepared using methods of organic synthesis. Compounds are condensed using liquid nitrogen (b.p.
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