TELLURIUM CATIONS BY LEWIS ACID-BASE REACTIONS - SYNTHESES AND CRYSTAL-STRUCTURES OF (TE-4(2+)(ZR2BR-10(2-) AND (TEBR-3+)(ZR2BR-9-)

ZrBr4 reacts with Te2Br in a sealed evacuated ampoule at 210-degrees-C in quantitative yield to afford (Te4(2)+)(Zr2Br10(2)-) as blue-black, moisture-sensitive crystals. The crystal-structure determination shows, that (Te4)(Zr2Br10) consists of planar, nearly square Te4(2)+ and Zr2Br10(2)- ions, that form edge-sharing double octahedra. Both ions possess crystallographic 2/m (C2h) symmetry. At temperatures above 250-degrees-C (Te4)(Zr2Br10) decomposes with cleavage of Te - Te bonds into (TeBr3+)(Zr2Br9-), which forms yellow, hygroscopic crystals. (TeBr3)(Zr2Br9) can also be obtained by the reaction of two equivalents of ZrBr4 with TeBr4 at 260-degrees-C. The crystal structure is built of Zr2Br9- ions, that form face-sharing double octahedra, and of pyramidal TeBr3+ ions. Each TeBr3+ ion exhibits three Te - Br contacts to two different Zr2Br9- ions, resulting in a strongly deformed octahedral coordination for the Te atom. The Zr2Br9 double octahedra and the TeCl6 octahedra are connected by common edges and corners to infinite chains.