Nomenclature, for coordination compounds

Esters. Esters of inorganic acids are named as the salts for example, ( 113)2804, dimethyl sulfate. However, if it is desired to specify the constitution of the compound, the nomenclature for coordination compounds should be used. 

Any scheme of nomenclature for coordination compounds should offer a broad general pattern capable of wide extension. These rules provide suitable names for compounds to which this pattern of nomenclature has not been applied previously. 

The last four examples that we have provided illustrate that while a good start has been made toward a rational nomenclature for coordination compound stereochemistry, many challenges still remain. 

This overview covers some of the rules for naming simple inorganic compounds. There are additional rules, and some exceptions to these rules. The first part of this overview discusses the rules for deriving a name from a chemical formula. In many cases, the formula may be determined from the name by reversing this process. The second part examines situations in which additional information is needed to generate a formula from the name of a compound. The transition metals present some additional problems therefore, there is a section covering transition metal nomenclature and coordination compounds. 

Next, one should note that the same protocol that had been developed in the proposed nomenclature for "organic" compounds is readily applied to coordination compounds in inorganic chemistry namely, the monocyclic compound which I.U.P.A.C. calls dichloro[N,N-dimethyl-2,2 -thiobis(ethylamine) -S,N ]platinum (II) (Figure 20), may be named, without resorting to different prefixes for the number two (di- and bis-) and without the prime symbol, as ... 

The systematic naming, or nomenclature, of coordination compounds can be complicated to apply, but it is essential to have some familiarity with the basic rules of nomenclature and to be able to work out the structure of a compound from its systematic name. Only a very brief summary of the rules for naming of coordination compounds can be given here, but more detailed accounts are available elsewhere. " ... 

A systematic system of nomenclature exists for coordination compounds of metal ions. 

He incorporated these into his suggestions for the nomenclature of coordination compounds. The result was names such as these (33) ... 

General Items Involved in Coordination Nomenclature. In following the development of nomenclature practices for coordination compounds, one needs some frame of reference to compare the continuities and changes. This is perhaps most easily done by reference to a set of principles or rules which has been used by the author on other occasions (10, 11, 13). We shall follow the changes in the statement of a given rule while the specific field covered by the rule does not change. Prior to the time of Werner, there was no basis for a systematic nomenclature. The rules and practices established by Werner might be expressed as a number of simple rules (13). 

The pattern of chemical combination represented by coordination compounds is one of common occurrence. The adoption of a basic plan of nomenclature for this fundamental pattern of chemical combination is desirable. The basic philosophy underlying the various schemes for the naming of coordination compounds is reviewed briefly. The causes of apparent contradictions are discussed. The practices for the nomenclature of coordination compounds suggested by the Commission on the Reform of Inorganic Chemical Nomenclature of the International Union of Chemistry (1940) previously were formulated into a set of rules (1948). These rules are now modified in the light of criticism and further study and are extended to cover situations not previously included. Examples are given to show how the practices prescribed by the rules may be extended. 

Most students of chemical nomenclature will agree that a broad general pattern which is capable of extension to diverse types of compounds is preferable to a number of specific patterns of limited extension. Inasmuch as most compounds of higher order can and should be looked upon as coordination compounds, coordination compounds encompass an extremely broad field. The development of a satisfactory scheme of nomenclature for these compounds may solve many nomenclature problems. If coordination compounds represent a fundamental pattern of chemical combination, there should be a sound basic plan for the nomenclature of this broad class of compounds. 

Another suitable group of compounds for testing the adaptability of the nomenclature patterns for coordination compounds is that presented by the aminopolyacids. The metal derivatives of some of these are of great interest today so much so, in fact, that ethylenediaminetetraacetic acid has become an important article of commerce. There have been, as yet, no serious efforts to name the metal coordination compounds of these acids. The following are suggested ... 

The carbonyls and their derivatives are undoubtedly coordination compounds. However, their nomenclature has never followed that for coordination compounds. The following examples will show the ease with which this can be accomplished ... 

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. 

Additive nomenclature treats a compound or species as a combination of a central atom or central atoms with associated ligands. The particular additive system used for coordination compounds (see Chapter IR-9) is sometimes known as coordination nomenclature although it may be used for much wider classes of compounds, as demonstrated for inorganic acids (Chapter IR-8) and organometallic compounds (Chapter IR-10) and for a large number of simple molecules and ions named in Table IX. Another additive system is well suited for naming chains and rings (Section IR-7.4 see Example 6 below). 

In the stereochemical nomenclature of coordination compounds, the procedure for assigning priority numbers to the ligating atoms of a mononuclear coordination system is based upon the standard sequence rules developed for chiral carbon compounds (the Cahn, Ingold, Prelog or CIP rules6, see Section IR-9.3.3.2). 

The nomenclature of coordination compounds is described in detail in Chapter IR-9. A brief summary of the construction of formulae of coordination compounds is given here. Many polyatomic compounds may conveniently be treated as coordination compounds for the purpose of constructing a formula. 

For the accepted nomenclature and notation regarding absolute configuration designations for coordination compounds, see (a) "I.U.P.A.C. Information Bulletin No. 33",... 

We introduce the nomenclature used for coordination compounds. We see that coordination compounds exhibit isomerism, in which two compounds have the same composition but different structures, and then look at two types structurai isomers and stereoisomers. 

Some metal complexes have a coordination number of 5. One such complex is Fe(CO)5, which adopts a trigonal bipyramidal geometry (see Figure 9.8). (a) Write the name for Fe(CO)5, using the nomenclature rules for coordination compounds. 

The recommended lUPAC nomenclature rules for coordination compounds are as follows ... 

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 coordination compounds is introduced in two sections. Here we consider the basics of naming ligands (including multidentate, ambidentate, and bridging) that occur in simple neutral as well as ionic coordination compounds. In Chapter 3, we will concentrate on the nomenclature for compounds for which a variety of isomers are possible. 

Before a uniform system of nomenclature could be developed for coordination compounds, some compounds were named after the chemists who originally prepared them. In addition, since the nature of the bonding in these compounds was not clear, the structural formulae for these compounds look somewhat strange to us. For example, a compound known as Erdmanns Salt was written... 

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