CO2 silylation at a tucked-in iron(II) complex.

Abstract

Carbon dioxide (CO₂) capture and valorization remain central challenges in sustainable chemistry due to the persistence of CO₂ as a major greenhouse gas. Herein, we describe the functionalization of a CO₂-activated organometallic complex, [(Cp*-CO₂)Fe(diphosphine)] (1; Cp* = C₅Me₅) in which CO₂ is selectively incorporated into the Cp* ligand framework. Treatment of 1 with trimethylsilyl chloride (TMSCl) affords [{Cp*-C(O)-O-TMS}Fe(diphosphine)Cl] (2) via silylation of the Fe-O(CO₂) linkage. Chloride abstraction using NaBPh₄ generates the putative complex [{Cp*-C(O)-O-TMS}Fe(diphosphine)]⁺ (3), featuring a labile dative R₂C=O→Fe interaction that is readily displaced by acetonitrile to give [{Cp*-C(O)-O-TMS}Fe(diphosphine)(NCCH₃)]⁺ (4). Reduction of the ester functionality in 2 using HBCy₂ (Cy = cyclohexyl) provides access to new borylated complexes. Collectively, these results demonstrate the cooperative capture and stepwise CO₂ functionalization at a common Cp* ligand framework.