Cyclotrisilicate

Cyclotrisilicate is a term used in inorganic chemistry to describe a cyclic silicate unit composed of three silicate tetrahedra linked to form a ring. The anion [Si3O9]6− consists of three SiO4 tetrahedra joined by corner-sharing oxygen atoms, producing a ring of nine oxygens. In this arrangement each silicon atom remains tetrahedrally coordinated, and the structure features three Si–O–Si bridges with the remaining oxygens completing the tetrahedral coordination.

Charge and composition: Treating silicon as +4 and oxygen as −2 gives an overall charge of −6 for [Si3O9]6−. The ring is typically stabilized in salts by countercations such as Na+, K+, or other metal ions, leading to formulations like M6[Si3O9], where six cations balance the anion’s charge.

Occurrence and preparation: Cyclotrisilicate species can arise in alkaline silicate solutions and in certain crystalline salts during the condensation and rearrangement of smaller silicate units. They are often investigated as intermediates or as isolated ions in crystallized salts, depending on conditions such as cation size and solution chemistry.

Relation to other silicates: Cyclotrisilicate is part of a broader family of cyclic silicate anions, which also includes larger rings (for example, cyclotetrasilicate [Si4O12]8−). The study of these species helps illuminate patterns of silicate polymerization and the diversity of ring-formed anions in solution and solid-state chemistry.

See also: Silicate chemistry, silicate anions, cyclotetrasilicate.