Preparation, structure, and properties of new ternary rhenium arsenides and phosphides with metal-metal bondings

The M₂Re₅As₁₂ arsenides (M = Fe, Co, Ni) and the Co₂Re₅P₁₂ phosphide were synthesized. The unit cell is orthorhombic with space group Pnnm and contains two formula units. The X-ray structure of Ni₂Re₅As₁₂ was studied from three-dimensional single-crystal counter data and was refined down to R = 0.048 for 637 independent reflections. The structure can be described as built up from two different structural domains; the first one is the marcasite type and shows As---As pairs and linear Re---Re chains, the second one consists of Re₄ clusters with common edges linked to terminal Ni atoms. A nearly temperature-independent paramagnetism and p-type metallic conduction were observed from the magnetic and electrical measurements. Also observed in this new family of compounds were the resistivities along and perpendicular to the c axis and their anisotropic behavior.