η3-Allyl and η3-methallyl complexes of molybdenum react with aldehydes to give homoallylic alcohols in preparative yields when water is used as a proton source, but the scope of the reaction is narrowed in the case of the η3-crotylmolybdenum complex by the formation of both transposed and nontransposed products.Key words: molybdenum, allylation, chelate model, transposition.