Antimony compounds are widely used as catalysts for the synthesis of the commercially important polymer poly(ethyleneterephthalate) by polycondensation of bis(hydroxyethyl)terephthalate. The precise nature of the antimony catalysts is, however, unknown. The present study has been conducted with a view to determining the nature of the catalytic species by structurally characterizing antimony ethylene glycolate compounds and related catecholate derivatives, namely [Sb-2(OCH2CH2O)(3)](n), [Sb(OCH2CH2O)(OAc)](n), [pySb(1,2-O2C6H4)](2)O, and [pyH][Sb(1,2-O2C6H4)(2)].