CO 2 silylation at a tucked-in iron(II) complex

Carbon dioxide (CO 2 ) capture and valorization remain central challenges in sustainable chemistry due to the persistence of CO 2 as a major greenhouse gas. Herein, we describe the functionalization of a CO 2 -activated organometallic complex, [(Cp*–CO 2 )Fe(diphosphine)] ( 1 ; Cp* = C 5 Me 5 ) in which CO 2 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(CO 2 ) linkage. Chloride abstraction using NaBPh 4 generates the putative complex [{Cp*–C(O)–O–TMS}Fe(diphosphine)] + ( 3 ), featuring a labile dative R 2 C=O→Fe interaction that is readily displaced by acetonitrile to give [{Cp*–C(O)–O–TMS}Fe(diphosphine)(NCCH 3 )] + ( 4 ). Reduction of the ester functionality in 2 using HBCy 2 (Cy = cyclohexyl) provides access to new borylated complexes. Collectively, these results demonstrate the cooperative capture and stepwise CO 2 functionalization at a common Cp* ligand framework.