Hydroboration of the (C₅Me₅)Fe(1,2-Ph₂PC₆H₄) System To Derive Hydridoborate and Hydridosilicate Complexes

The synthesis and characterization of hydridoborate and hydridosilicate iron half-sandwich complexes derived from activation of HBpin with an N2-bridged dimer [Cp*Fe(1,2-Ph2PC6H4)]2(μ-N2) (1, Cp* = C5Me5–) are reported. The reaction appears to proceed by hydroboration of the Fe-based metallacycle to give a 16-electron iron(II)-hydride intermediate, presumably Cp*FeH(Ph2PC6H4Bpin), which is able to capture a HBpin or H2SiPhR (R = Ph or H) molecule through Fe-H cooperation, resulting in Cp*Fe(η3-H2Bpin)(Ph2PC6H4Bpin) (2) and Cp*Fe(η3-H2SiHPhR)(Ph2PC6H4Bpin) (R = Ph, 3a; H, 3b) complexes. Density functional theory calculations showed that those complexes exhibit intriguing Fe–H–E nonclassical features (E = B or Si), and the nature of Fe-η3-H2E interactions can be rationalized as unusual hydrido-borane and -silane complexes, that is, (H)Fe-η2-H–E. This has been shown by straightforward substitution of the HBpin moiety of hydridoborate with silane, affording hydridosilicate complexes.