Ligands coordination-type nomenclature

As in the nomenclature of other inorganic compounds, specific rules are followed for naming coordination compounds. In general, the number and type of ligands attached to the metal ion are specified, as is the oxidation state of the metal ion. 

The nomenclature of simple coordination compounds is developed in a set of rules for referring to ionic and neutral ligands, the number of each type of ligand, and the oxidation state of the metal. A number of examples of naming compounds and writing formulas are given. 

The ultimate dream for an excellent evaluation would be to delineate the dimensional space (16e) of catalytic reactions. The three principal axes in such a space could be (1) the d" configuration of the metal, (2) the coordination number, and (3) the element group (i.e., in the new ACS nomenclature 3,4,... 12). In terms of the dimensional space many of the transformations considered would occupy a limited volume. In a more elaborate n-dimensional space one could add ligand type and other considerations to better represent the whole set of transformations. 

From these examples the rules of nomenclature are apparent. The central atom (like Fe, Cu, Co, Ag) is followed by the formula of the ligand (CN, NH3, H20, S203), with the stoichiometric index number, (which, in the case of monodentate ligands is equal to the coordination number). The formula is placed inside square brackets, and the charge of the ion is shown outside the brackets in the usual way. When expressing concentrations of complexes, brackets of the type will be used to avoid confusion. In the name of the ion, first the (Greek) number, then the name of the ligand is expressed, followed by the name of the central atom and its oxidation number (valency). 

Two forms of the /i-T>, T> -bridging allenyl ligand have been identified. The most common form for both homo- and heterometallic dimers is that in which the internal double bond (C -Cjb) forms the interaction (type H). However, the previously unknown bonding type I in which the external double bond (C -Cy) is coordinated in an manner to the adjacent metal center has been established (38b). The bimetallic compounds [Ru2(CO)6(/A-PPh2)(M-i . i -PhC=C=CPh2)] and [Ru2(CO)6(/i-PPh2)(/i-T, Tj -PhC=C=CH2)] are of structural types H and I respectively, and provide an informative comparison. These types can be distinguished by the nomenclature fi-r), r) a,p and which specifies the internal... 

Additive nomenclature was originally developed for Werner-type coordination compounds, which were regarded as composed of a central atom (or atoms) surrounded by added groups known as ligands, but many other types of compound may also be conveniently given additive names. Such names are constructed by placing the names of the ligands (sometimes modified) as prefixes to the name(s) of the central atom(s). 

---