RuxSey and Rux, materials were synthesised in two solvent media: Xylene (Xyl) and 1, 2-dichlorobenzene (DCB) from Ru3(CO)12 and elemental selenium. The results of a comparative study of the carbonyl chemical precursor decomposition are reported. The presence of selenium accelerates and modifies the decomposition of the carbonyl precursor converging in a cluster-like ruthenium chalcogenide compound. The evolution of the chemical reaction, monitored ex situ by FTIR points towards different chemical pathways depending on the solvent used. The electrocatalytic properties of RuxSey and Rux for the molecular oxygen reduction are also discussed.