A Facile Route for the Synthesis of Polycationic Tellurium Cluster Compounds: Synthesis in Ionic Liquid Media and Characterization by Single-Crystal X-ray Crystallography and Magnetic Susceptibility

An innovative soft chemical approach was applied, using ionic liquids as an alternative reaction medium for the synthesis of tellurium polycationic cluster compounds at room temperature. [Mo2Te12]I-6, Te-6[WOCl4](2), and Te-4[AlCl4](2) were isolated from the ionic liquid [BMIM]Cl/AlCl3([BMIM](+): l-n-butyl-3-methylimidazolium) and characterized. Black, cube-shaped crystals of [Mo2Te12]I-6, which is not accessible by conventional chemical transport reaction, were obtained by reaction of the elements at room temperature in [BMIM]Cl/AlCl3. The monoclinic structure (P2(1)/n, a = 1138.92(2) pm, b = 1628.13(2) pm, c = 1611.05(2) pm, beta = 105.88(1) degrees) is homeotypic to the triclinic bromide [Mo2Te12]Br-6. In the binulear complex [Mo2Te12](6+), the molybdenum(III) atoms are eta(4)-coordinated by terminal Te-4(2+) rings and two bridging eta(2)-Te-2(2-) dumbbells. Despite the short Mo ... Mo distance of 297.16(5) pm, coupling of the magnetic moments is not observed. The paramagnetic moment of 3.53 mu(B) per molybdenum(III) atom corresponds to an electron count of seventeen. Black crystals of monoclinic Te-6[WOCl4](2) are obtained by the oxidation of tellurium with WOCl4 in [BMIM]Cl/AlCl3. Tellurium and tellurium(IV) synproportionate in the ionic liquid at room temperature yielding violet crystals of orthorhombic Te-4[AlCl4](2).