n124792SE Academic Article uri icon

abstract

  • The early transition metals, especially Zr, Hf, Hb and Ta, exhibit a metal-rich chemistry that is often surprising in its structural and physical aspects. Unfamiliarity with this chemistry is illustrated by the discovery of several new binary compounds in the Ta-S, Ta-Se, Ta-Te, and Hf-Te systems within the past few years. Some striking differences observed between the metal-rich chalcogenides of Zr and Hf or between Nb and Ta challenge basic presumptions about the similarity of these congeneric pairs. The factors controlling the structural anisotropy of a new class of tetragonal layered compounds that includes Ta2Se, Ta2-xNbxS, Hf3Te2, and ZrZTe (Z Si, Ge, Sn) are discussed. Strongly early-late transition intermetallic bonding leads to the formation of an expanding class of compounds that includes Ta9M2S6 (M Fe, Co, Ni), Ta11M2Se8 (M Fe, Co, Ni), Ta8NiSe8 and the newly discovered hafnium tellurides, Hf8MTe6 (M Mn, Fe, Co, Ni, Ru) and Hf5MTe3 (M Fe, Co). Our efforts to dismantle solid-state Zr-halide cluster compounds is described. Ambient temperature molten salts help us achieve the controlled excision of [(Zr6Z)CL18]n- from solid state precursors; we describe the applications of electronic and NMR spectroscopies in characterizing clusters in solution. Finally, we discuss bonding in metal-rich systems, with particular emphasis on localized bonding descriptions for metalmetal bonds in extended metal-linked networks. Such localized descriptions increase our understanding of otherwise anomalous properties and illuminate the artificiality of separate "metallic" and "covalent" bonding concepts. 1995.

published proceedings

  • Journal of Alloys and Compounds

author list (cited authors)

  • Hughbanks, T.

publication date

  • January 1, 1995 11:11 AM