An organopalladium chemical dosimeter of Hg(2+) that methylates Hg(2+), undergoing a colour change in 1 : 1 ethanol-water with submicromolar sensitivity, gives rise to an aqua-palladium complex that is methylated by MeHg(+) in the presence of a dithiol compound, undergoing another colour change, thus making the system suitable for the naked-eye detection of Hg(2+) and MeHg(+), two environmentally important species of Hg(2+).

Square-planar complexes [PdCl{κ 2 -(RN = CHC 6 H 4 PPh 2 )RЈ}] (RЈ = Cl; R = 4-CH 3 C 6 H 4 , 1a; R = 2-CH 3 OC 6 H 4 , 1b; R = 2-HOC 6 H 4 , 1c; RЈ = CH 3 ; R = 4-CH 3 C 6 H 4 , 2a; R = 2-CH 3 OC 6 H 4 , 2b; R = 2-HOC 6 H 4 , 2c) have been prepared and characterized. In complexes 2a-c only formation of one isomer was observed. The Pd-methyl bond arranges in a cis position to the phosphane fragment of the P,N chelating ligand. Reaction of complexes 2a-c in acetonitrile with AgBF 4 led to removal of the chlorido ligand and coordination of acetonitrile