Generative and Stabilizing Processes in Tin-Palladium Sols and Palladium Sol Sensitizers

An extensive study of sol systems produced by the reduction of solvated Pd by Sn 2+ is presented. We show that the reaction is initiated by the formation of a polynuclear Sn‐Pd complex, which is autoreductive, yielding sol particles of a Sn‐Pd alloy core with a stabilizing layer of Sn 2+ ions. The role of the Sn 2+ stabilizing layer in controlling particle size is discussed in detail. We apply the knowledge of these systems to understand similar processes occurring in commercial Pd sol systems used for sensitizing insulating surfaces for electroless plating. The chemistry of the sensitizing layer generated by these systems has also been studied. The sol sedimentation rate has been studied by centrifugation. Most of the investigation has been carried out via Mössbauer spectroscopy; precise isomer shift parameters for a number of Sn‐Pd compounds are reported.