SOME SUBSTITUTIONAL CHEMISTRY IN KNOWN TERNARY AND QUATERNARY CHALCOGENIDES

New ternary and quaternary transition-metal chalcogenides have resulted from substitutional chemistry of known phases. Ta//2Ni//3S//8 and Ta//2Pt//3Se//8 have been synthesized and characterized by single-crystal X-ray techniques. These compounds adopt the Nb//2Pd//3Se//8 structural type. Hence in Ta//2Ni//3S//8 Ni occupies both square-planar and square-pyramidal sites as similarly does Pt n Ta//2Pt//3Se//8. The electrical conductivity of Ta//2Ni//3S//8 establishes its semiconducting behavior. Ta has been substituted for Nb in the Nb//2Pd//0//. //7//1Se//5 type to yield Ta//2Pd//0//. //8//9S//5 which has been characterized by single crystal X-ray techniques. The square-planar Pd sites in the van der Waals' gap of this layer structure are 78. 6(4)% occupied.