Naming of silsesquioxane

The English name silsesquioxane comes from Latin and can be translated as: silicium (silicon), sesqui (one and a half), oxygenium (oxygen), which means that the ratio of atoms to silicon atoms is one and a half. The use of system names for polyhedra silsesquioxanes can be cumbersome, therefore the literature uses the nomenclature for siloxanes. This classification distinguishes five silicon atoms (see figure below). Type "M" symbol one connected with three organic groups and an atom connected. A silicon atom of type "D" is linked to two atoms, type "T" is linked to three atoms, and type "Q" is linked to four atoms manually. Si–O connections can form siloxane (Si–O–Si) or silanol (Si–OH) groups. To distinguish them, a superscript is used, which defines the number of Si–O–Si bonds formed by the silicon atom, eg T³ represents a silicon atom containing one organic group and three siloxane bonds. Polyhedral silsesquioxanes have T³ type silicon atoms. The number of silicon atoms is given in subscript. The designation T₈R₈ or R₈T₈ means octameric hexahedral silsesquioxane containing eight organic side groups or hydrogen atoms. Formula Me₈T₈ refers to the octamethyloctaasilsesquioxane compound with the systematic name octamethyl-pentacyclo [9.5.1.1^3,9.1^5,15.1^7,13] octasiloxane presented in figure below.

 Connection types for silicon atoms (R = hydrogen, alkane or phenyl)

 

 

Structure of octamethyloctasilsesquioxane (Me₈T₈)