Controlled Expansion of a Strong‐Field Iron Nitride Cluster: Multi‐Site Ligand Substitution as a Strategy for Activating Interstitial Nitride Nucleophilicity

Abstract

Multimetallic clusters have long been investigated as molecular surrogates for reactive sites on metal surfaces. In the case of the μ₄ -nitrido cluster [Fe₄ (μ₄ -N)(CO)₁₂ ]^- , this analogy is limited owing to the electron-withdrawing effect of carbonyl ligands on the iron nitride core. Described here is the synthesis and reactivity of [Fe₄ (μ₄ -N)(CO)₈ (CNAr^Mes2 )₄ ]^- , an electron-rich analogue of [Fe₄ (μ₄ -N)(CO)₁₂ ]^- , where the interstitial nitride displays significant nucleophilicity. This characteristic enables rational expansion with main-group and transition-metal centers to yield unsaturated sites. The resulting clusters display surface-like reactivity through coordination-sphere-dependent atom rearrangement and metal-metal cooperativity.