COMPOUNDS WITH SIS2 ISOELECTRONIC ANION-1 -INFINITY[ALX4 2(3-)] AND ANION-1-INFINITY[INP4/2(3-)] - SYNTHESIS, CRYSTAL-STRUCTURES AND VIBRATIONAL-SPECTRA OF NA3[ALX2],K2NA[ALX2] AND K3[INP2] (X = P, AS)/

The title compounds were prepared from stoichiometric mixtures of the elements or from alkali metals (Na, K), NaX (KX) and MX (M = Al, In; X = P, As) at 1000 K. The crystal structures (Ibam, No. 72) are charact erized by infinite chains of edge sharing tetrahedra infinity1[MX4/2(3 -)] (M = Al, In; X = P, As) which are isoelectronic to SiS2. The vibra tional spectra can be interpreted with respect to the symmetry P(2/m 2 /c) 4(2)/m-D4h of the isolated polymeric chain infinity1[MX4/2(3-)]. T he assignment of the observed frequencies is supported by a normal coo rdinate analysis using the fragment method.