Double complex salts of Pt and Pd ammines with Zn and Ni oxalates – promising precursors of nanosized alloys

Double complex salts [M(NH3)4][M′(Ox)2(H2O)2] · 2H2O (M = Pd, Pt, M′ = Ni, Zn) were synthesized by combination of solutions containing corresponding cations [M(NH3)4]2+ and anions [M′(Ox)2(H2O)2]2−. The salts obtained were characterized by IR spectroscopy, thermal analysis, powder and single crystal X-ray diffraction. The prepared compounds are isostructural and crystallize in the orthorhombic crystal system (space group I222, Z = 2). Thermal decomposition of the salts in helium or hydrogen atmosphere at 200–400 °C results in formation of nano-sized bimetallic powders. Depending on the phase diagram of the respective bimetallic system and temperature conditions, they can be single phase or multiphase products. In particular, thermal decomposition of double complex salts [M(NH3)4][Zn(Ox)2(H2O)2] · 2H2O (M = Pd, Pt) results in formation of PdZn and PtZn intermetallic compounds, correspondingly. Decomposition of [Pd(NH3)4][Ni(Ox)2(H2O)2] · 2H2O affords a disordered solid solution Pd0.5Ni0.5. Disordered Pt0.5Ni0.5 was obtained from [Pt(NH3)4][Ni(Ox)2(H2O)2] · 2H2O in helium atmosphere, while in hydrogen atmosphere – a two-phase mixture of disordered Pt0.5Ni0.5 and ordered PtNi. In all cases crystallite sizes of bimetallic particles varied within 50–250 Å.