PREPARATION, STRUCTURES, AND PROPERTIES OF NIOBIUM CHALCOGENIDE HALIDES, NBX2Y2(X=S,SE-Y=CL,BR,I)

The preparation of the compounds NbX2Y2 (X = S, Se; Y = Cl, Br, I). including that of large single crystals, by chemical transport techniques is reported. Most of these compounds exist in a triclinic low-temperature form and a monoclinic high-temperature form. The crystal structures of triclinic low-temperature NbSe2Cl2 and monoclinic NbS2Cl2 are reported; both structures consist of cage-shaped units of Nb2X4 which are linked together by the Cl atoms to form sheets parallel to the a, b planes. Both the Nb and the X atoms are present in pairs which indicates that the compounds can be formulated as Nb4+2(X2)2-22Y-4, in agreement with XPS spectra. The presence of Nb4+ in pairs explains the observed diamagnetic and semiconducting properties of NbX2Y2. The preparation and some properties of MoS2Cl2 (orthorhombic) are also given. © 1979.