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? 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.