Nomenclature main group elements

An area of current development is the nomenclature of organometallic compounds. Organometallic compounds of Main Group elements can, to a first approximation, be considered to be derivatives of hydrides, and the methods of substitutive nomenclature can be applied. Even then, the accessibility of different oxidation states, as with phosphorus(iii) and phosphorus(v), introduces complications. Transition metal organometallic compounds are even more difficult to treat, and the development of a unified, self-consistent and accepted and applied nomenclature is not easy. Witness the different ways (k, t and italicised symbols) for denoting donor atoms in ligands. 

Note that Examples 10-14 above show how one may easily name transition metal compounds that have been named as acids in the past. Names such as permanganic acid, dichromic acid, etc., are not included in the present recommendations because they represent an area where it is difficult to systematize and decide what to include, and where the names are not needed for organic nomenclature, as opposed to the corresponding acid names for acids of main group elements. 

IR-10.3 Nomenclature of organometallic compounds of the main group elements IR-10.3.1 Introduction... 

Sometimes it may be necessary or preferable to consider a parent hydride in which several (four or more) skeletal carbon atoms of a hydrocarbon have been replaced by main group elements. In this method of skeletal replacement the heteroatoms are designated by the a terms of replacement nomenclature (Table X) cited in the order given by Table VI and preceded by the appropriate locant(s). The rules for locant numbering are specified in Section IR-6.2.4.1 and this nomenclature is fully described in Sections P-21.2 and P-22.2 of Ref. 3. 

Hypervalent compounds of main-group elements are often classified using the Martin-Arduengo N—X—L nomenclature, where N represents... 

Scheme 5 Nomenclature and classification of main-group-element H-bonds.

Molecules that contain the atoms Li and Be need to have 2p functions, and Na and Mg need 3p functions added to the basis set in order to prevent the compounds from becoming too ionic. Likewise, elements in the second-row and heavier main group elements of the Periodic Table need d-type functions added to the basis set. For second-row elements, the split-valence basis set 3-21G is used. The in the nomenclature indicates that d-type orbitals are available for second-row elements only. 

In this article the author has been using the traditional ylide-ylene nomenclature as well as the modern phosphorane-arsorane-stiborane formalism. No attempt has been made to discriminate between one or the other of these modalities because it is felt that both offer a sufficiently clear description of at least those species that are derived from the main Group Vb elements. (Fortunately no Nli,s or BiR5 had to be given names.). However, when this procedure was followed with the vanadium, niobium, and tantalum compounds, an interesting problem arose because the authors... 

---