Access to Hybrid Sandwich Complexes of Early Transition Metals with Cp/Cp* and <i>cyclo</i>-E₅ Ligands (E = P, As)

Since the groundbreaking discovery of [Cp*Fe(η⁵-P₅)] (Cp* = η⁵-C₅Me₅), the exploration of hybrid inorganic sandwich complexes combining cyclopentadienyl-type ligands and <i>cyclo</i>-E₅ rings (E = P, As) has been an active research area of inorganic chemistry, for extensive reactivity studies involving the production of numerous derivatives and supramolecular aggregates. However, synthetic limitations have hitherto restricted their accessibility to group 8 transition metals. Herein, we present a facile and versatile approach to access such 16e-18e complexes of early transition metals, [CpV(η⁵-E₅)]^1-/2-, [CpCr(η⁵-E₅)]^-, and [Cp*Mn(η⁵-P₅)]^- (E = P, As; Cp = η⁵-C₅H₅). By utilizing the Zintl phase precursor K₃E₇ as a reductant, these new complexes can be rapidly synthesized via one-pot reactions at ambient temperature within 1 h. This method enables the preparation of diverse derivatives from [CpV(η⁵-E₅)]^2-, including the oxidative coupling product [(CpV)₂(μ,η^4:4:1:1-P₁₀)]^2- as well as its niobium congener [(CpNb)₂(μ,η^4:4:1:1-P₁₀)]^2-, and the addition rearrangement products [(CpV)₆P₁₀]^2- and [(CpV)(μ,η^4:5-As₅)Mn(η³-As₃)]^2-. The Zintl-driven reduction strategy provides a viable approach to expand hybrid sandwich complexes beyond group 8 metals and enables the exploration of novel inorganic architectures.