Abstract
Metathesis reactions of Ag[C(CN)(3)] with anhydrous YbCl(3) dissolved in water combined with stoichiometric amounts of the alkali-metal salts A[C(CN)(3)] (A = Na or K) yield the non-isotypic tetragonal compounds NaYb[C(CN)(3)](4) (P4/nnc with a = 1188.37(9) pm, c = 1232.41(9) pm) and KYb[C(CN)(3)](4) (P4/nbm with a = 1179.26(9) pm, c = 668.73(5) pm). Both crystal structures contain a three-dimensional framework (Niggli formula: 3∞{(Yb[C(CN)(3)](8/2))(-)}) with Yb(3+) in square antiprismatic coordination of terminal nitrogen atoms (d(Yb-N) = 241-242 pm) from eight planar star-shaped tricyanomethanide anions [C(CN)(3)](-). The Na(+) or K(+) cations occupy vacancies, which provide them with a tetrahedral coordination sphere of nitrogen (d(Na-N) = 239 pm vs. d(K-N) = 276 pm) from four [C(CN)(3)](-) anions. This difference results from secondary contacts with the central carbon atoms (d(Na-C) = 361 pm vs. d(K-C) = 367 pm) of four different [C(CN)(3)](-) units, which do not contribute to NaYb[C(CN)(3)](4), but effectuate a lot in the case of KYb[C(CN)(3)](4). The Raman spectrum recorded for NaYb[C(CN)(3)](4) corroborates the presence of a pseudo-D(3h)-symmetric tricyanomethanide anion [C(CN)(3)](-) and the absence of water.