The [Ru(CN)(6)](3-) ion is synthesized in aqueous solution and isolated as [Ph(4)AS](3)[Ru(CN)(6)].2H(2)O (1). Compound 1 crystallizes as orange needles in the monoclinic space group P2(1)/n with cell parameters a = 11.346(2) Angstrom, b = 23,107(5) Angstrom, c = 25.015(5) Angstrom, beta = 99.55(3)degrees, V = 6467.1(22) Angstrom(3), Z = 4. The octahedral anion has Ru-C bond lengths in the range 2.023(6)-2.066(6) Angstrom. DFT calculations reproduce experimental geometries for [M(CN)(6)](3-) (M = Fe, Ru) equally well and yield significantly higher spin densities on the cyanide ligands in [M(CN)(6)](3-) (M = Ru, Os) than in [Fe(CN)(6)](3-).