Two novel molybdenum-containing organic complexes based on 3,4-dihydroxy-3-cyclobutene-1,2-dione ("squaric acid"), 1-phenyl-1-ethanamine and 1,3-diamino-2-propanol (DAP), respectively, have been synthesized in aqueous medium and characterized by infrared (FT-IR) spectroscopy, thermogravimetric (TGA) and elemental analyses. The catalytic activities and selectivities of these complexes in the epoxidation of cyclohexene with t-butylhydroperoxide (TBHP) were, approximately, the same as those of similar complexes prepared previously in the same manner. (C) 2003 Elsevier B.V. All rights reserved.