SYNTHESIS AND CRYSTAL-STRUCTURE OF A CALCIUMCARBIDE CHLORIDE CONTAINING A C-3(4)- UNIT, CA3CL2C3

Ca3Cl2C3 was prepared from calcium, CaCl2 and graphite in sealed tantalum capsules. Red, transparent crystals were obtained from heating the mixture to 900-degrees-C (for one day) and annealing afterwards at 780-degrees-C for three days. The compound forms a layered structure (Cmem, Z = 4, a = 384.24(9) pm, b = 1340.7(3) pm, c = 1152.6(3) pm, R = R(w) = 0.036 for 481 independent intensities) with alternating stacks of double layers of Ca2+ and monolayers of Cl-. The double layers of calcium contain allylenide ions, C3(4-). The latter exhibit C2v symmetry, a bond angle (C-C-C) of 169.0(6)-degrees and a C-C separation of 134.6(4) pm.