Central atom concepts oxidation states

The concept of oxidation states is best applied only to germanium, tin and lead, for the chemistry of carbon and silicon is almost wholly defined in terms of covalency with the carbon and silicon atoms sharing all their four outer quantum level electrons. These are often tetrahedrally arranged around the central atom. There are compounds of carbon in which the valency appears to be less than... 

One final concept needs to be mentioned. In many compounds, two central atoms can be bridged by a direct bond between them, without any bridging ligand. This bond occupies a position in the coordination shell without using a lone pair. Essentially, the two central atoms share pairs of electrons, one electron coming from each central atom in most cases. This is reflected in the corresponding oxidation states. 

Truly, the redox reaction concept in its simplest form, transfer of one or several electrons between two species, is much easier to apply to the central atoms of inorganic complexes and relatively simple covalent inorganic compounds with their well-defined oxidation states than to the carbon atoms of organic molecules. Nevertheless oxidation states of the latter can be defined using very simple rules (see, e.g. Hendrickson et al., 1970) and immediately reveal the possible redox nature of any transformation at a carbon atom. It is also true that redox mechanisms other than electron transfer—hydrogen atom or hydride transfer, oxygen transfer, displacement, etc.—should by their very... 

---