Exploratory synthesis of reduced rare-earth-metal halides, chalcogenides, intermetallics : New compounds, structures, and properties

A new direction in reduced rare-earth-metal (R) compounds opened up when tantalum (and niobium) were adapted to use as virtually faultless containers for these reactions, as these gave immediate access to many new metal-rich phases and structures. Examples are summarized for the new binary dihalides (e.g., Pr, Nd, Dy, Ho, Tm), metallic diodides (Sc, La, Ce, Gd), and metal–metal bonded chains (Sc, Y, Gd, Lu) that were so discovered. Furthermore, a large array of condensed metal cluster, chain, and sheet halides arise when a stoichiometric amount of a diverse variety of nonmetal or metal atoms is included to serve as an interstitial, the earliest examples originating with traces of common impurities. A change in anion charge type to telluride affords a whole new regime of condensed metal-rich cluster compounds and structures, including such remarkable examples as (Sc, Gd, Dy)2Te, Lu11Te4, Lu8Te, and Sc6PdTe2. Also, a number of novel Zintl phases, interstitial derivatives of the type R5Ge3Z, quasicrystals, and their approximants are generated in other intermetallic systems. Generalities in structures and bonding are described along the way.