Square brackets coordination compounds

Free Radicals. In the formula of a polyatomic radical an unpaired electron(s) is(are) indicated by a dot placed as a right superscript to the parentheses (or square bracket for coordination compounds). In radical ions the dot precedes the charge. In structural formulas, the dot may be placed to indicate the location of the unpaired electron(s). 

Coordination compounds contain a complex. In general, a complex may be recognized because it is enclosed in square brackets [ ]. The square brackets are omitted when the actual structure of the complex is uncertain. 

Coordination compounds. [In the formula of a coordination entity.] the symbol of the central atom(s) is placed first, followed by the ionic and then the neutru] ligands. Square brackets are used to enclose the whole coordination entity whether charged or not. This practice need not be used for simple species such us the common oxoanions (NO, NOT, SO -, OH-, etc.). Enclosing marks are nested within the square brackets as follows [()]. U<) , [()]>]. [( [()] ]]. etc. 

Compounds of known composition but uncertain polymeric structure can be conveniently named by selecting a suitable subunit and prefixing poly to the compositional coordination name of the subunit. Bridging and other bonding notations are not generally employed, unless limited bonding and specific structural detail is known about the internal structure of the polymer subunit. The poly prefix is not italicized and the name of the subunit given after poly is enclosed in square brackets. For examples see Table 23. 

A complex compound is compound formed between reactants of which the valencies are already formally saturated, e.g. CoCl2 + 2 Et4N+Cl v (Et4N)2[CoCl4]. All three compounds are stable individually. We generally use square brackets to denote the coordination complex. 

To write the formula of compounds containing complex ions we make use of square brackets to represent the complex ion, e.g., [Ni. (NH3)6] Br2. In it [Ni (NH3)6]2+ is the complex ions. It indicates that six NH3 are attached directly to Ni. Such complex compounds are called coordination compounds. 

A] representing the concentration of A in mol dm, and coordination complexes, e g. [Co(NH, )J This presents a potential source of confusion when defining equilibrium constants for coordination compounds since often only one set of brackets is used. Usually the function of the square bracket is clear from the context in which it is used, but for clarity in this text, two sets of square brackets will be usixJ v/hen appropriate. Since equilibriurri constants are dimensionsless it is the convention to divide concentrations in an equilibrium constant expression by a standard concentration, mol dm. ... 

In several of the examples below, substitutive names (see Chapter IR-6) are also given. In some cases, however, there is no parent hydride available for the construction of a substitutive name (see Examples 9 and 11). Note also that the formulae given below in square brackets are coordination compound-type formulae with the central atom listed first. 

A coordination compound is any compound that contains a coordination entity. A coordination entity is an ion or neutral molecule that is composed of a central atom, usually that of a metal, to which is attached a surrounding array of other atoms or groups of atoms, each of which is called a ligand. Classically, a ligand was said to satisfy either a secondary or a primary valence of the central atom and the sum of these valencies (often equal to the number of ligands) was called the coordination number (see Section IR-9.1.2.6). In formulae, the coordination entity is enclosed in square brackets whether it is charged or uncharged (see Section IR-9.2.3.2). 

Many organometallic compounds of groups 1 and 2 exist in associated molecular form (as aggregates) or contain structural solvent, or both. However, their names are often based solely on the stoichiometric compositions of the compounds, unless it is specifically desired to draw attention to the extent of aggregation or the nature of any structural solvent, or both (see Example 3 below). In the examples below, note how the different types of name reflect the different structural content implied by the formulae shown. As usual, the formulae enclosed in square brackets designate coordination entities. 

The formulae of coordination compounds and complexes are not enclosed in square brackets [71JEN] (Rule 7.21). Exceptions are made in cases where square brackets are required to distinguish between coordinated and uncoordinated ligands. 

A typical coordination compound appears in Figure 22.7A the coordination compound is [Co(NH3)6]Cl3, the complex ion (always enclosed in square brackets) is [Co(NH3)6] " , the six NH3 molecules bonded to the central Co are ligands. 

As a general rule, polyolefins do not tend to form very stable compounds in which only one double bond is coordinated to a given metal atom. There is a strong tendency for at least a second double bond to become coordinated via displacement of some other ligand. Thus we have the annexed reactions, where species in square brackets are not isolable ... 

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