Si2O5

Si2O5, commonly referred to as disilicon pentoxide, is a binary silicon oxide with the chemical formula Si2O5. It is considered a suboxide relative to silicon dioxide (SiO2) and is not known as a stable bulk compound under ordinary conditions. In silicate chemistry, Si2O5 units are used to describe fragments or motifs that can appear during condensation of silanol groups or dehydration of silicic acids. The species is more commonly encountered as a transient gas-phase molecule or as part of larger silicon-oxygen networks than as a discrete solid.

Structure and bonding in Si2O5 are discussed in terms of two silicon centers connected by oxide bridges within a silicate framework. The exact arrangement depends on the environment, and the bonding is often described as covalent with potential hypervalent character at silicon centers. Because of its suboxide nature, Si2O5 tends to exist only under specialized conditions or as part of larger condensed structures rather than as a standalone material.

Occurrence and preparation: Si2O5 has been detected in gas-phase studies of silicon oxide clusters and can be generated in situ by dehydration or fragmentation of larger silicon-oxygen species. It can also be invoked conceptually in models of silica polymerization, where chains or rings incorporating Si2O5 units can form as intermediates or fragments within more extensive networks.

See also: silicon dioxide, silicate, silicate networks, disilicate (Si2O7).