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

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.