The crystal structure of Ta6S

Abstract

The crystal structure of Ta6S has been determined from single-crystal X-ray diffraction data. The compound crystallizes in the monoclinic space group C2/c with unit-cell dimensions a = 14.16, b = 5284, c= 14.79/~ and fl= 118.01 °. The unit cell contains eight formula units. Refinement of the structure with three-dimensional data was performed by a least-squares treatment of the positional parameters and the isotropic temperature factor coefficients. The metal grouping in the Ta6S structure is unlike that in other known metal-rich chalconide structures with the exception of TazS, to which it is closely related. The structure can be viewed as chains of body-centered pentagonal antiprisms of Ta atoms sharing faces in one direction and interconnected via sulfur atoms in the other two directions. The sulfur atoms are coordinated by seven tantalum atoms, six of which are arranged in distorted trigonal prisms. The seventh coordinated tantalum atom occurs off a rectangular face of the trigonal prism, a very common coordination configuration for sulfur and phosphorus in metal-rich compounds.