The compound Pd.sub.3 P.sub.2 S.sub.8 in the form of crystals having trigonal symmetry can be made by heating together the appropriate elements of binary compounds thereof providing the atomic ratio of S to P is greater than unity. The compound is useful as a semiconductor and as a catalyst for the replacement of aromatic hydrogen with carbonyl chloride groups.
The method of preparing Pb.sub.x Mo.sub.y S.sub.z where x = 0.8-1.1, y = 4.5-5.6, and z = 5.4-7.2 comprising the steps of mixing commercial reagent grade powders of the reactants, heating in a sealed, evacuated reaction vessel to a temperature of 950.degree.-1150.degree. C, maintaining the temperature until the compound is formed, and then cooling the compound at a controlled rate not in excess of 4.degree. C per minute.
