Siloxides are chemical compounds with the formula R3SiOM, where R is usually an organic group and M is usually a metal cation. Also called silanoates, they are derived by deprotonation of silanols. They also arise by the degradation of siloxanes by base: R3SiOSiR3 + 2 NaOH → 2 R3SiONa + H2O Cleavage of cyclic siloxanes affords siloxides: (Me2SiO)3 + MeLi → Me3SiOSiMe2OSiMe2OLi These anions function as ligands for metal ions, forming complexes similar to metal alkoxides. Sodium trimethylsiloxide is useful for generating metal complexes by salt metathesis reactions. A very bulky siloxide is tert-butyl3SiO−, sometimes called silox. Siloxides are weaker net donors than alkoxides because pπ-d donation has to compete with backbonding from the oxygen atom into the low-lying Si-C σ* orbitals. References Organosilicon compounds