A Facile Method for the Synthesis of Binary Tungsten Iodides

The preparation of tungsten iodides in large quantities is a challenge because these compounds are not accessible using an easy synthesis method. A new, remarkably efficient route is based on a halide exchange reaction between WCl6 and SiI4. The reaction proceeds at moderate temperatures in a closed glass vessel. The new compounds W3I12 (W3I8⋅2 I2) and W3I9 (W3I8⋅1/2 I2) containing the novel [W3I8] cluster are formed at 120 and 150 °C, and remain stable in air. W3I12 is an excellent starting material for the synthesis of other metal‐rich tungsten iodides. At increasing temperature these trinuclear clusters undergo self‐reduction until an octahedral tungsten cluster is formed in W6I12. The synthesis, structure, and an analysis of the bonding of compounds containing this new trinuclear tungsten cluster are presented. A halide exchange reaction between WCl6 and SiI4 yields a new stable tungsten iodide W3I12 (W3I8⋅2 I2) with the [W3I8] cluster (see picture), which can be used in the synthesis of other tungsten iodides. The synthesis and the structure and bonding situation of compounds with this new trinuclear cluster are presented.