Flash Communication: Well-Defined Paramagnetic Polyhydrido-Bridged Iron–Iridium Clusters

Polyhydrido transition metal complexes are a constant source of interest due to their variety in bonding and reactivity. Yet, well-defined paramagnetic polyhydrido systems are relatively rare given their instability. Herein, we extend the protonolysis reactivity of the Brønsted acidic Cp*IrH₄ polyhydride toward transition metal silylamides. Specifically, we report the synthesis and characterization of a polyhydrido diiron tetrairidium paramagnetic cluster, [Fe-(Cp*IrH₃)₂]₂, <b>1</b>, from the reaction between Fe-(HMDS)₂(THF) and Cp*IrH₄. Attempted reduction of this complex with potassium graphite yields instead an anionic species, K-[Fe-(Cp*IrH₃)₃], <b>2</b>, in a proposed disproportionation mechanism. Complex <b>2</b> can be independently synthesized in good yields upon treating <b>1</b> with K-[Cp*IrH₃]. Attempts to synthesize Fe-(III) analogues from the oxidation of <b>1</b> or <b>2</b> failed, with oxidation occurring at the Ir centers. Likewise, reactions between Fe-(III) precursors and iridium polyhydride species consistently yield complex <b>1</b>. This highlights the unexpected driving force toward this very stable tetrairidium diiron paramagnetic polyhydride complex reported in this work.