Synthesis, Reactivity, and Structural Characterization of the Nonclassical [MTe7] n - Anions (M = Ag, Au, n = 3; M = Hg, n = 2)

Several tellurometalates of the general formula [MTe7] n - (n = 2, 3) have been isolated as salts of organic cations by reaction of suitable metal sources with polytelluride solutions in DMF. The [HgTe7]2- anion has the same structure in both the NEt4 + and the PPh4 + salts except for a minor change in the ligand conformation. The [AgTe7]3- and [HgTe7]2- anions contain metal atoms coordinated in trigonal-planar fashion to η3-Te7 4- ligands. The central Te atom of an η3-Te7 4- ligand is coordinated to the metal atom and to two Te atoms in a “T”-shaped geometry consistent with a hypervalent 10 e- center. The planar [AuTe7]3- anion may best be described as possessing a square-planar AuIII atom coordinated to an η3-Te5 4- ligand and to an η1-Te2 2- ligand. The reaction of [NEt4] n [MTe7] (M = Hg, n = 2; M = Au, n = 3) with the activated acetylene dimethyl acetylenedicarboxylate (DMAD) has yielded the products [NEt4] n [M(Te2C2(COOCH3)2)2] (M = Hg, n = 2; M = Au, n = 1). The metal atoms are coordinated to two Te(COOCH3)CC(COOCH3)Te2- ligands, for M = Hg in a distorted tetrahedral fashion and for M = Au in a square-planar fashion.