Si–Cl σ-Bond Cleavage by an Fe(0) Complex with Two Steps of One-Electron Transfer toward Hydrosilane Formation from Tetrachlorosilane

Iron catalysts exhibit unique reactivity that has not been found in precious metal catalysts. Herein, a new strategy for strong Si-Cl σ-bond cleavage of tetrachlorosilane (SiCl₄) was successful using [{Fe(PNNP)}₂(μ-N₂)] (PNNP = 2,9-bis((diphenylphosphino)methyl)-1,10-phenanthroline). The resulting oxidative addition product [Fe(SiCl₃)(Cl)(PNNP)] was fully identified, establishing the first example of Si-Cl σ-bond cleavage using an air-sensitive iron(0) complex. Theoretical study revealed that Si-Cl σ-bond cleavage occurs with radical character through two steps of single-electron transfer from [Fe(PNNP)] to the Si-Cl σ* antibonding orbital, which differs from usual concerted oxidative addition. This σ-bond cleavage reaction was successfully applied to HSiCl₃ formation from SiCl₄ and 1,10-dihydroanthracene via hydrogen atom transfer (HAT). Thus, we succeeded in performing Si-Cl σ-bond cleavage using the Fe(0) complex and its application to hydrosilane synthesis from SiCl₄ using a mild hydrogen source. This iron(0) complex is expected to be active as catalyst for other difficult reaction.