We have studied the formation of the ''sandwich'' type heteropolyanion
, [Pd-4(PW9O34)(2)](10-), by the reaction of the thermolized trilacuna
ry heteropolytungstophosphate Na-8[HPW9O34].26H(2)O and the PdCl2 solu
tions. In order to determine the optimum synthesis conditions, a spect
rophotometric study has been undertaken at different pH and temperatur
e values and a conductometric and photocolorimetric study has been mad
e to determine the stoichiometric combination ratio metal cation: hete
ropolyligand.