Synthesis, Crystal Structure and Optical Spectra of Yb₂[CN₂]₃

Red-orange, transparent single crystals of Yb 2 [CN 2 ] 3 [trigonal, R3̄c (no. 167), a = 630.02(3) and c = 2947.4(2) pm, Z = 6] are obtained by the reaction of Yb, Sn, Zn[CN 2 ] and NaN 3 in arc-welded Nb ampoules at 1100 K. The title compound exhibits characteristic C-N bond lengths and angles [d(C-N) = 122.7(3) pm and ∡(N-C-N) = 178.4(5)°, respectively] within the [N=C=N] 2 − unit as well as the expected fundamental frequencies in its optical spectra (Raman: νs = 1338; δ = 643 / 683 / 695 cm −1 ; IR: ν as = 2005 / 2037; δ = 640 / 679 cm −1 ). Since Yb 2 [CN 2 ] 3 adopts a corundum-type structure, Yb 3+ is octahedrally coordinated by six N atoms of different [CN 2 ] 2− anions [d(Yb-N) = 228.6(3) and 233.4(3) pm, 3× each] and every [CN 2 ] 2− group has four Yb 3+ as next neighbours which form a distorted tetrahedron.