Tributyltin oxide

Tributyltin oxide (TBTO), or bis(tri-n-butyltin)oxide, is an organotin compound chiefly used as a biocide (fungicide and molluscicide), especially a wood preservative. Its chemical formula is C24H54OSn2. It has the form of a thin, colorless to pale yellow liquid with melting point -45 °C, boiling point 180 °C, and slight water solubility (20 ppm). It is combustible and soluble in organic solvents.

It is available under names AW 75-D, Bio-Met TBTO, Biomet, Biomet 75, BTO, Butinox, C-SN-9, Hexabutyldistannoxane, Hexabutylditin, and others.

Tributyltin oxide is a potent skin irritant.

Tributyltin compounds had been used as marine anti-biofouling agents. Concerns over toxicity of these compounds (some reports describe biological effects to marine life at a concentration of 1 nanogram per liter) have led to a world-wide ban by the International Maritime Organization. It is now considered a severe marine pollutant.