The water-soluble backbone heterometallic polymer {[(PTA)(2)CpRu--CN-RuCp(PTA)(2)--NiCl3]}(n) (2) is synthesized using a reproducible and robust method and fully characterized by X-ray single crystal diffraction. The Ru-Ru-Ni polymer is found to be stable in the solid state and soluble in water. Nuclear magnetic resonance (NMR) and light scattering studies show that the polymer is stable in water for several days in air.