Abstract
The layered niobium cluster halide, α-Nb 3Cl 8, offers a potentially rich chemistry because of its morphology and electronic structure. Substitution of chloride by telluride, driving forces for mixed crystal formation, and possible structural distortions on intercalation in α-Nb 3Cl 8 are probed using both experimental and theoretical techniques. The compound Nb 3TeCl 7 has been synthesized in quantitative yield from the reactants Nb, NbCl 5, and Te and has been structurally characterized by single-crystal X-ray diffraction. Nb 3TeCl 7 crystallizes in the space group P 3 m1 (no. 164); a=6.8985(12) A ̊ ; c=12.6351(26) A ̊ ; Z=2; R=0.0238; wR=0.0392 . The structure consists of Nb 3 triangular clusters singly capped by μ 3-Te atoms. Physical measurements and semiempirical electronic structure calculations demonstrate the closed subshell nature of the bonding in this compound. In addition, these calculations predict a structural instability for Nb 3Cl 8-type halides when the cluster valence electron concentration rises above 7.5 electrons per Nb 3 cluster, and provide a rationale for the observed homogeneity width within the α-Nb 3− x Cl 8 system (0⩽ x⩽0.5).
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