Activation of Dihydrogen and Phenylsilane with Fe(−II) Carbonyl Complexes Enabled by a Lewis Acid in the Secondary Coordination Sphere

Transition metal carbonyl anions, featuring metals in negative oxidation states, constitute an important family of complexes. These species typically react with organic and inorganic (pseudo)halides and demonstrate strong basicity, nucleophilicity, and reducing power. However, their reactivity toward nonpolar or weakly polar substrates, such as dihydrogen and silanes, remains largely unexplored. Here, we report the synthesis and characterization of two Fe(-II) carbonyl dianions featuring borane pendants with varying tether lengths in the secondary coordination sphere [(L)Fe(CO)₃]²⁻ (L = Ph₂P(CH₂)nBBN; n = 2, 3; BBN = 9-borabicyclo[3.3.1]nonyl). Reactivity studies indicate that these species can activate dihydrogen and phenylsilane, forming Fe(0) hydride and silyl complexes with borohydride units. Subsequent hydride transfer from the borane pendants to unsaturated substrates has also been demonstrated. This work provides a novel strategy to enhance the reactivity of transition metal carbonyl anions toward nonpolar or weakly polar substrates and opens new avenues for the catalytic applications of these types of compounds.