Elements substituent groups

Element substituent group names are formed by adding the suflix -io to the stem of the name (compare anion name formation). 

A major feature of the polyphosphazene skeleton is its ability to resist fire and combustion due to the inorganic elements constitutive of its structure [44,387, 388,459,460]. Moreover, the action of skeletal nitrogen and phosphorus atoms can be enhanced by inserting additional inorganic elements (F, Cl, Br, J, B, metals, etc.) in the substituent groups [459,460]. 

When two hydrogens on a benzene ring are replaced hy other elements (disuhstitution), there are three possible configurations, as shown here, where X = a substituent group, either the same or different. 

These names are used in oi anic substitutive nomenclature for situations in which the substituent group is joined to the parent skeleton by a single element-carbon bond. 

When the position of a substituent group has not been established or is in doubt, the doubtful position may be indicated by x or followed by ( ). In some cases the probable positions are given in parentheses, eg 4(or 7)-aminobenzotriazole. Where two ways are commonly used to indicate the position of groups or elements in a molecule, one of the alternative ways is usually placed in parentheses directly after the letter or symbol designating the position, eg 2 (or o). and a (or 1H). This is done to avoid repeating the whole name... 

Steric factors play a marked role in inter- and intra-molecular coordination of compounds of heavy elements of group 14. The complexation requires an approach of the donor and acceptor centres to an optimal distance. If these centres are shielded by bulky substituents, the complexation becomes difficult or impossible. Thus, for example, the tributylalkoxystannanes BusSnOR are monomeric for any R. At the same time the dibutyl-dialkoxystannanes Bu2Sn(OR)2 are monomeric only when containing bulky R substituents such as CH2CHMe2 or CMe3. The butylalkoxystannanes BuSn(OR)3 are monomeric only when the alkyl substituents R are not smaller alkyl radicals (Me, Et, Pr)79. 

Elements of Group IV of the Periodic System have been used in the last decade as organometallic precursors for aryl halogenide syntheses56. The mechansim of electrophilic demetalation of these precursors can be demonstrated by the simplified scheme shown in equation 14. The positive inductive effect of the alkyl substituents promotes the formation of intermediate (20) by increasing the electron density at the ipso carbon atom. 

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