The structures of alkalides and electrides. III. Structure of potassium cryptand[2.2.2] natride

Abstract

K+ClsH36N206.Na -, Mr = 438.59, ortho- rhombic, Fdd2, a= 15.769 (7), b= 25.245 (7), c = 13.818 (13) A, V = 5501 (3)/~3, Z = 8, Ox = 1-06 g cm -3, A(Mo Kte) = 0.71073/~, /~ = 2-3 cm -I, F(000) = 2592, T = 206 (4) K, final R = 0.021 for 1198 (I>3tr(/)) of 1275 unique reflections. The structure is completely different from that of the corresponding electride, K+(C222).e -, which shows evidence of paired electrons. This is additional evi- dence that the natride ion, Na-, does not form dimers, Na 2-, or chains as are seen in some K-, Rb- and Cs- crystals. Introduction. After the structure of the electride K+(C222).e - was determined and its magnetic properties were interpreted by invoking electron spin pairing (Huang, Faber, Moeggenborg, Ward & Dye, 1988; Ward, Huang & Dye, 1988), it was predicted that the structure of the corresponding natride, K+(C222).Na -, would be different from that of the electride since it was felt that dimers, Na~- would