Communication: The precise control of the amount of catalytic palladium deposited on a substrate as an ultrathin film can be achieved if the films are prepared using the Langmuir-Blodgett technique. The high solubility of the dibenzylideneacetone derivative shown in the figure facilitates this approach, producing films stable at room temperature but which decompose depositing metallic palladium at the melting point of the complex, 165-degrees-C.