The Diammoniates of Dipotassiumtetraethinylozincate and -cadmate: K2M(C2H)4·2NH3 (M = Zn, Cd)

By reaction of KC2H and K2Zn(CN)4 in liquid ammonia, the diammoniate K2Zn(C2H)4.2NH3 was obtained. K2Cd(C2H)4.2NH3 was synthesized by reacting KC2H, Cd(NH2)2, and acetylene in liquid ammonia. The crystal structures of the air and temperature sensitive compounds were determined by X-ray single crystal diffraction at low temperatures (T = 170 K). Both compounds crystallize in the monoclinic space group 121 a (No. 15) with Z= 4. K2Zn(C2H)4.2NH3: a = 7.289(1) A, b = 12.765(2) A, c = 14.066(2) A, (beta) - 98.11(2). K2Cd(C2H)4-2NH3: a = 7.444(1) A, b = 12.619(3) A, c = 14.304(2) A, (beta) = 98.94(1)°. Characteristic structural motifs are tetrahedral [M(C2H)4]^2- fragments (M = Zn, Cd) and zigzag chains of edge sharing distorted (C2H)6 octahedra centered by potassium ions. These zigzag chains are connected by a second type of crystallographically distinct potassium ions that also bind to two ammonia molecules.