Structure and properties of double complex salts [Co(NH3)6][Fe(CN)6] and [Co(NH3)6]2[Cu(C2O4)2]3

Double complex salts (DCSs) [Co(NH₃)₆][Fe(CN)₆] (I) and [Co(NH₃)₆]₂[Cu(C₂O₄)₂]₃ (II) and complex [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O (III) are synthesized and investigated by single crystal XRD, crystal optics, and elemental analysis. The crystalline phases of I, II, and III (R-3, P2₁/c, and Pnnm space groups respectively) have the following crystallographic characteristics: a = 10.9804(2) ?, b = 10.9804(2) ?, c = 10.8224(3) ?, V = 1130.03(4) ?³, Z = 3, d _x = 1.65 g/cm³ (I); a = 9.6370(2) ?, b = 10.2452(2) ?, c = 13.2108(3) ?, V = 1932.90(9) ?³, Z = 2, d _x= 1.97 g/cm³ (II), and a = 11.7658(3) ?, b = 11.7254(3) ?, c = 14.1913(4) ?, V = 1304.34(5) ?³, Z = 2, d _x = 1.68 g/cm³ (III). This paper investigates the products of DCS thermolysis in a hydrogen atmosphere: the intermetallic compound CoFe with the bcc parameter a = 2.852 ? for I and a heterogeneous mixture of Co and Cu in the decomposition of II. The coordinated CN⁻ and C₂O₄²⁻ groups then turn into NH₃, hydrocarbons, and CO₂. The dominant hydrocarbon is methane.