Enhancing the Reactivity of an Aromatic <i>cyclo</i>‐P₅ Ligand via Electrophilic Activation

Electrophilic activation of the aromatic cyclo-P₅ ligand in [Cp*Fe(η⁵-P₅)] is demonstrated to drastically enhance its reactivity towards weak nucleophiles. Unprecedented functionalized, contracted as well as complexly aggregated polyphosphorus compounds are accessed utilizing [Cp*Fe(η⁵-P₅Me)][OTf] (A), highlighting the great potential of this underexplored mode of reactivity. Addition of carbenes to A affords novel 1,2- or 1,1-difunctionalized cyclo-P₅ complexes [Cp*Fe(η⁴-P₅(1-L)(2-Me)][OTf] (L=IDipp (1), ^EtCAAC (2), IⁱPr (3 b)) and [Cp*Fe(η⁴-P₅(1-IⁱPr)(1-Me)][OTf] (3 a). For the first time, the much smaller IMe₄ leads to the contraction of the cyclo-P₅ ligand and formation of [Cp*Fe(η⁴-P₄(1-IMe)(4-Me)] (4). DFT calculations shed light on the delicate mechanism of this type of reaction, which is reinforced by the experimental identification of key intermediates. Even the comparably weak nucleophile IDippCH₂ reacts with A to form [Cp*Fe(η⁴-P₅(1-IDippCH₂)(1/2-Me)][OTf] (6 a/b), highlighting its explicitly more reactive nature. Moreover, exposure of A to IDippEH (E=N, P) leads to a unique aggregation reaction affording [{Cp*Fe}₂{μ₂,η^4:3:1-P₁₀Me₂(IDippN)}][OTf] (8) and [{Cp*Fe}₂{μ₂,η^4:1:1:1-P₁₁Me₂(IDipp)}][OTf] (9), respectively.