Two series of complexes with general formula M(n-butoxicle)(4-x)(maltolate)(x), where M = Ti or Zr and x = 0-4, were studied as catalyst for transesterification and esterification, in order to obtain methyl esters. The compounds containing different ratios of maltolate and n-butoxide ligands were synthesized from the reaction of maltol (3-hydroxy-2-methyl-4-pyrone) and n-butoxide metal precursors. All complexes, containing maltolate as ligand, were very efficient as catalyst in esterification, mainly those based in zirconium. In counter part, the catalysts here displayed very poor activity for transesterification. (C) 2008 Elsevier B.V. All rights reserved.