Sb−Sb Interactions in the Hafnium-Rich Antimonide Hf₆TiSb₄

(Hf,Ti)7Sb4 is accessible via arc-melting of suitable mixtures of Hf, Ti, and HfSb2. Its crystal structure is the first representative of a new structure type, as was determined by single-crystal analysis for Hf7-xTixSb4 with x = 1.05(7) ≈ 1. Hf6TiSb4 crystallizes in the monoclinic space group P21/c, with the lattice dimensions a = 841.0(1), b = 1102.9(1), c = 1099.3(1) pm, and β = 111.13(1)° (Z = 4). All seven independent metal sites are statistically occupied by different mixtures of hafnium and titanium, forming a three-dimensional network of metal atoms M which includes the Sb atoms in its (capped) square antiprismatic voids. The metal substructure can be described on the basis of semiregular 488 nets. Besides numerous M−Sb and M−M bonds, a nonlinear Sb3 unit is present with bonding Sb−Sb interactions. Extended Hückel calculations, performed on the hypothetical model structure Hf7Sb4, point to metallic properties.