To give a more or less exact definition of what is a complex compound of modern chemistry has to rely on the main provisions of the coordination of the theory, which was proposed by A. Werner in 1893. More complexity of the issue lies in the diversity and multiplicity of the most varied chemicalcompounds falling within the definition of the complex.
In general, complex compounds - chemical substances, which included a number of complex particles.Until now, science has no strict definition of "complex species."Often used the following definition: a complex particle understand complex particles, which can exist independently in the crystal and in solution.It consists of the other elementary particles, which in turn have the ability to live independently.Also often the definition of complex particles fall complex chemical species in which all or part of connection are formed on the donor-acceptor principle.
common feature, which possess all the complex compounds is the presence in their structure of the central atom, received the name of "complexing".Given the diversity that these compounds have a talk about some general features of this element is not necessary.Often the complexing agent is an atom forming metal.But this is not a strict feature: there are complex compounds in which the central atom is an atom of oxygen, sulfur, nitrogen, iodine and other elements representing bright nonmetals.Speaking of charge complexing agent, it can be said that most of it is positive, and in the scientific literature called metal center, but there are examples where the central atom and have a negative charge, and even zero.
Accordingly, isolated groups of atoms or individual atoms, which are located around the complexing agent, called ligands.This may be particles which before entry into the complex compound is a molecule, for example, water (H2O), carbon monoxide (CO), nitrogen (NH3) and others, it may also be anions OH-, PO43-,Cl-, hydrogen or a cation H +.
Trying to classify the complex compounds according to the type of charge of the complex separates the chemical compounds in the cationic complexes, which are formed around a positively charged ion neutral molecules.Anionic complexes are also available, in which the complexant is an atom with a positive oxidation state.Simple and complex anions are ligands.A separate group can be identified neutral complexes.Their formation takes place through the coordination of around neutral atom molecules.Also in this category of complex compounds include compounds formed by the simultaneous coordination around a positively charged ions and molecules, and negative ions.
Given the number of seats held by the so-called ligands in the coordination sphere, it is determined monodentate, bidentantye and polydentate ligands.
Preparation of complex compounds in different ways allows the classification of the nature of the ligand.Among them distinguish ammines, in which the ligands are represented by molecules of ammonia aqua complexes, wherein the ligand is water, carbonyls - carbon monoxide acts as a ligand.Furthermore acidocomplexes exist in which a central atom surrounded by acidic residues.If he is surrounded by hydroxide ions, the invention relates to a hydroxycomplexes.
Complex compounds play an important role in nature.Without them impossible livelihoods of living organisms.Also, the use of complex compounds in human activity allows complex manufacturing operations.
Analytical chemistry, extraction of metals from ores, electroplating, production of paints and varnishes - it's just a short list of industries which have been used complex chemicals.