Synthesis, characterization and reactivity toward small molecules of a diiron tetrahydrido bridged complex

Abstract

Under reduction conditions, a tetrahydrido bridged diiron complex [Cp″Fe(μ-H)4FeCp″] (1, Cp′′ = η5-C5iPr4H) was smoothly synthesized by facile H2 activation. In the presence of MeCN as solvent, two hydrides were reductively eliminated as H2 and the other two hydrides were inserted into the C≡N bond to give two imido bridges. Unexpectedly, when 1 was treated with 2 equiv. of tBuNC, two bridging hydrides were coordinatively replaced by two isocyanide groups and ejected as H2. Meanwhile, the other two hydrides remained between the two iron centers for maintaining the binuclear framework. In addition, interaction of 1 with elemental sulfur (S8) resulted in the formation of sulfide-bridged diiron complex accompanied with H2 liberation from four bridging hydrides. The interaction manifolds of this molecular system with nitrogenase related substrates may be helpful to understand the key role of the two {Fe−H−Fe} subunits in the “E4” state during the activation and transformation of substrates promoted by nitrogenase.