SYNTHESIS AND CRYSTAL-STRUCTURE OF HF2TE

Hf2Te was prepared by are-melting appropriate compressed mixtures of H fTe2 and hafnium. The structure of the new hafnium-rich telluride was determined by means of powder diffractometry, R-B = 0.0565. Hf2Te adop ts a Nb2Se-type structure, monoclinic, space group C2/m, Z = 8, Pearso n symbol mS24, a = 1516.3(2) pm, b = 370.26(4) pm, c = 1006.4(1) pm, b eta = 90.50(1)degrees. The structure comprises pairwise interpenetrati ng columns of trans-face-shared centred Hf-9 cuboids. The columns form puckered slabs which are interconnected by homo- and heteronuclear bo nds. Tellurium atoms are one-sidedly coordinated by six hafnium atoms. The coordination configurations about the two distinct tellurium atom s represent Hf6Te hypho-fragments of a tri-capped trigonal prismatic H f9Te close-cluster. Characteristic features of four other M(2)Q struct ure types are elucidated. The valence electron concentration available for metal-metal bonding together with the cohesive energy of the resp ective metal are found to control the formation of the various M(2)Q m etal partial structures.