Compositional nomenclature addition compounds

IR-1.5.3.2 Compositional nomenclature IR-1.5.3.3 Substitutive nomenclature IR-1.5.3.4 Additive nomenclature IR-1.5.3.5 General naming procedures IR-1.6 Changes to previous IUPAC recommendations IR-1.6.1 Names of cations IR-1.6.2 Names of anions IR-1.6.3 The element sequence of Table VI IR-1.6.4 Names of anionic ligands in (formal) coordination entities IR-1.6.5 Formulae for (formal) coordination entities IR-1.6.6 Additive names of polynuclear entities IR-1.6.7 Names of inorganic acids IR-1.6.8 Addition compounds IR-1.6.9 Miscellaneous... 

Three systems are of primary importance in inorganic chemistry, namely compositional, substitutive and additive nomenclature they are described in more detail in Chapters IR-5, IR-6 and IR-7, respectively. Additive nomenclature is perhaps the most generally applicable in inorganic chemistry, but substitutive nomenclature may be applied in appropriate areas. These two systems require knowledge of the constitution (connectivity) of the compound or species being named. If only the stoichiometry or composition of a compound is known or to be communicated, compositional nomenclature is used. 

Compositional names are either of the stoichiometric type (which, furthermore, are of the binary type except in the case of homoatomic species) or of the addition compound type. Compositional nomenclature is used if little or no structural information is to be conveyed... 

During Werner s time compositional nomenclature for binary compounds had already been agreed upon in much the same way as today, and names such as manganese dichloride and manganese monooxide were in common use to express information about stoichiometric compositions only. For complex compounds, this type of nomenclature had simply b n extended as in the notational example 3 KCN,Fe(CN)3. Werner realized that diis notation could be modified to became a nomenclature including structural information, when this was available, and potassium hexacyanoferriate is his ingenious proposal (2). This is an example of what is today referred to as additive nomenclature or coordination nomenclature, as opposed to the substitutional nomenclature of organic chemistry. 

The nomenclature of a science ought to be distinguished for its clearness and simplimty but it is by no means easy to seoure these conditions in a science like chemistry, where the rapid progress of discovery necessitates the continual addition of new and the frequent alteration of old namea The chemical name of a substance should not only identity and indi-vidualise that substance, but it should also express the composition and constitution of the body, if a compound, to which it is applied. The first of these conditions is readily attained but the second is much more difficult to secure, inasmuch as our ideas of the constitution of chemical compounds—the mode in which they are built up as it were— require firequent modification. On this account all attempts to frame a perfectly consistent system of chemical nomenclature have hitherto been only partially successful. 

Inorganic additive nomenclature, however, names both simple and complex entities of more than 100 elements. Inorganic nomenclature also provides several degrees of complexity in order to enable a name for a compound to indicate empirical composition, molecular composition, composition and connectivity, and complete qualitative three-dimensional compound structure. 

Additive nomenclature1 is based on the combination of element names or roots of element names and/or ligand names. The simplest and oldest additive nomenclature is binary nomenclature that expresses two components, e.g. sodium chloride. The cationic or electropositive portion of the compound expressed in a binary name is the element name unchanged or a group name ending in -ium , and the anionic or electronegative portion of a compound expressed in the name ends in -ide, -ite or -ate. The proportions of cations and anions in neutral compounds are indicated by Stock numbers or simple or multiplicative prefixes (see Section 3.3.2). Additive nomenclature denotes composition. For examples see Table 1. 

Members of the staff of the technical library rapidly become experts on matters of nomenclature, and many questions concerning structure, formulas, and naming of compounds reach this group. Often the composition or manufacturer of a trade-named product is requested. In addition to such sources of information... 

Along with the theory of coordination, Werner proposed5 a system of nomenclature for coordination entities which not only reproduced their compositions but also indicated many of their structures. Werner s system was completely additive in that the names of the ligands were cited, followed by the name of the central atom (modified by the ending ate if the complex was an anion). Wemer also used structural descriptors and locants. The additive nomenclature system was capable of expansion and adaptation to new compounds and even to other fields of chemistry. 

The designation of central atom and ligands, generally straightforward in mononuclear complexes, is more difficult in polynuclear compounds where there are several central atoms in the compound to be named, e.g. in polynuclear coordination compounds, and chain and ring compounds. In each case, a priority order or hierarchy has to be established. A hierarchy of functional groups is an established feature of substitutive nomenclature Table VI shows an element sequence used in compositional and additive nomenclature. 

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