INOR 375 |
| The inorganic chemistry of intermetallic phases is particularly rich in novel compositions, structures, and bonding. Components of these diverse systems that have widely different electronegativities are valuable as they generate either counter-cations or -anions in the presence of the corresponding anionic or cationic intermetallic clusters or networks, our principal interests. Recent discoveries among both types will be described. Searches for new Zintl (classical valence) phases of the p-elements with active metal cations sometimes yield elegant polyanionic structures that exhibit significant electronic conductivities, extra bound cations and electrons, or other special situations. These illuminate novel alternatives to classic bonding. Moreover, inclusions of earlier p- or d-elements in such networks generally lead to polar phases that exhibit more delocalized bonding, higher coordination numbers, and lower electron counts per atom: 4.0 > e/a > ~ 2 or less, the last region including atypical “electron” phases. In some systems, incorporation of e-poorer elements (Li, Mg, Zn, Ag) into group 13 (triel) or other polyanion structures affords novel and significant electronic as well as structural effects. Gold substitutions yield especially rich chemistry of this nature. Novel structural variations also arise from size effects. These discoveries have led to new approaches for tuning certain structures to quasicrystals and their crystalline approximants and to larger structural regimes and regularities. Conversely, polar intermetallics containing a wide variety of polycationic networks of, e.g., rare-earth and, usually, late transition metals are obtained in the presence of relatively isolated, closed-shell spacer anions such as telluride or halide, “intermetallic salts” in essence. The polar nature of the inter-metal bonding in these networks appears to be particularly important. Recently characterized ternary tellurides of Y and of the heavier lanthanides (Gd, Er, Lu, etc.) that bind traditional transition-metal interstitials support the concept that greater inter-d-orbital mixing stabilizes these considerably. |
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ACS Awards to Inorganic Chemists
8:10 AM-12:50 PM, Monday, April 7, 2008 Morial Convention Center -- La Louisiane, Blrm. C, Oral
Division of Inorganic Chemistry |