BA2[TAN3] AND SR2[TAN3] - ISOTYPIC NITRIDOTANTALATES(V) WITH TETRAHEDRAL CHAINS 1-INFINITY[TAN2N2 2(4-)]/

Single crystals of Ba2[TaN3] (monocl., C 2/c (Nr. 15); a = 613.0(3), b = 1181.5(4), c = 1326.3(5) pm; beta = 9 1.1 (1)-degrees; Z = 8) were prepared from mixtures of Li and Ba (molar ratio 1:1) in tantalum cruc ibles and by reaction with nitrogen (I atm) at 1000-degrees-C. The cry stal structure (an isotype of Ba2[ZnO3]) contains infinite tetrahedral anions infinity1 [TaN2N2/24-] (Ta-N: 192.2(13)- 198.8(9) pm) which ca n be described as ''Zweier-Einfach-Kette''. Sr2[TaN3] (monocl., C2/c ( Nr. 15); a = 600.5(3), b = 1131.3(7), c = 1260.3(7) pm; beta = 91.71(6 )-degrees; Z = 8) was obtained as a yellow powder containing excess Sr 2N by reaction of Sr2N and Ta (molar ratio Sr: Ta = 4.5: 1) with nitro gen (1 atm) at 1000-degrees-C. The isotypic relationship to Ba2[TaN3] was confirmed by X-ray powder investigations.