An Investigation of Allyl‐Substituted Bis(Diphosphine) Iron Complexes: Towards Precursors for Cooperative CO₂ Activation

Abstract

In developing homogenous catalysts capable of CO2 activation, interaction with a metal center is often imperative. This work provides our primary efforts towards the cooperative activation of CO2 using a Lewis acidic secondary coordination sphere (SCS) and iron via a paired theoretical/experimental approach. Specifically, we report efforts towards [Fe(diphosphine)2(N2)] as a CO2‐coordinated synthon where diphosphine = 1,2‐bis(di(3‐cyclohexylboraneyl)propylphosphino)ethane) (P2BCy4) or its precursor, tetrakisallyldiphosphinoethane (tape). Initial efforts toward the {Fe(0)‐N2} complex were focused on deprotonation reactions of [Fe(diphosphine)2(H)(NCCH3)]+ and reduction of [Fe(tape)2Cl2]. In the latter case, a mixture of intramolecularly p‐bonded alkene and associated metallacyclic Fe(II)—H species were produced – heating this mixture provided the hydride as the major product. Notably, the interconversion of this pair counters that of related intermolecular reactions between [Fe(depe)2] (depe = 1,2‐bis(diethylphosphino)ethane) and ethylene, where hydride formation occurs subsequent to p‐coordination; this has been probed by theoretical calculations. Finally, reactivity of the metallacyclic {Fe(II)—H} complex with CO2 was probed, resulting in a pair of isomeric ferra(II)lactones.