BI4RUBR2 AND BI4RUI2 - 2 VARIETIES OF A COLUMN STRUCTURE WITH FACE-SHARING [RUBI8 2] SQUARE ANTIPRISMS/

Reaction of the elements yields black, lustrous, air insensitive cryst als of the subhalides Bi4RuI2 (tetragonal, I4/m, a=1183.9(2) pm, c=669 .7(2) pm, V=938.66 10(6) pm(3)) and Bi4RuBr2 (monoclinic, I112/m, a=12 11.9(2) pm, b=1072.6(2)pm, c=663.9(2)pm. gamma=91.63(1)degrees, V=862. 64. 10(6) pm(3)). The structures of the homootypic compounds contain ( 1)(infinity)[RuBi8/2] strands of face-sharing square antiprisms. Halog en atoms lie above the edges of alternate Bi-4 squares. Thereby chemic al bonding differs significantly within the two types of Bi-4 squares. Though the Ru atoms on the central axis of the strand of antiprisms f orm pairs, extended Huckel calculations give no evidence of Ru-Ru bond s.