A General and Flexible Synthesis of Transition-Metal Polyphosphides via PCl3 Elimination

We report a straight-forward, solvent-free moderate temperature synthetic method for the production of several phosphorus-rich transition-metal phosphides (orthorhombic FeP2, cubic CoP3, cubic NiP2, monoclinic CuP2, and monoclinic PdP2). Notably, this synthetic approach provides facile access to the high-temperature/high-pressure cubic phase of NiP2. The general synthetic strategy involves the direct reaction of anhydrous metal dichloride pressed pellets with molecular P-4 vapor or solid-solid reactions between the metal dichloride and red phosphorus that are intimately mixed into pellets. Both of these reaction strategies involve the evolution of a volatile PCl3 byproduct and produce crystalline MPx(x >= 2) at moderate temperatures of 500-700 degrees C. The pellets remain intact throughout the synthesis, and the macrostructure of the MP, products resembles that of the reactant pellets. By varying the phosphorus Source, the percentage of the pellet precursor mass that is retained in the final metal phosphide pellet products changes, which influences the morphology and microstructure of the final phosphide pellet.