Construction And Reactivity Of Thiolate-Bridged Ruthenium-Molybdenum Heteronuclear Complexes

This paper is built on the novel thiolate-bridged ruthenium-molybdenum complexes,the activation and transformation of various nitrogen-containing substrates were realized based on the unique reactivity of heterometallic sites.It provides an important experimental model for understanding the heteronuclear synergistic effect of nitrogenases active centers at the molecular level.Firstly,the reactivity of complex[Cp*Ru（μ-η⁴:η²-bdt）Mo Cl₂Cp*]（Cp*=η⁵-C₅Me₅,bdt=benzene-1,2-dithiolate）（1）with anhydrous hydrazine was investigated,and the results showed that the ruthenium-molybdenum center can realize the cleavage of the N–N and N–H bonds of hydrazine to generate a thiolate-bridged ruthenium-molybdenum heteronuclear complex[Cp*Ru（μ-η²:η¹-bdt）（μ-NH₂）Mo（N）Cp*]（5）featuring bridging amido and terminal nitrido ligands,this activation pattern of hydrazine has never been reported before.Complex 5can also be further protonated to give the thiolate-bridged ruthenium-molybdenum complex[Cp*Ru（μ-η²:η¹-bdt）（μ-NH₂）Mo（NH）Cp*]（6）with both bridging amido and terminal imido ligands.The above experimental results provide new insight for understanding the mechanism for the late stage of biological nitrogen reduction.Subsequently,the reactivity of thiolate-bridged ruthenium-molybdenum complexes with small nitrogenous molecules were investigated.Complex[Cp*Ru（μ-η⁴:η²-bdt）Mo Br₂Cp*]（2）reacted with azidotrimethylsilane can afford a rare thiolate-bridged heteronuclear nitride[Cp*Ru（μ-η²:η²-bdt）（μ-N）Mo Br Cp*]（7）.The reaction of complex 1 with two equivalents of sodium amide can give a thiolate-bridged ruthenium-molybdenum complex[Cp*Ru（μ-η¹:η²-bdt）（μ-NH₂）₂Mo Cp*]（8）containing two bridging amido ligands.In addition,complexes 5,7and 8 can be transformed into each other.Complex 5 can be prepared by the reactions of complex 7 with one equivalent of sodium amide or complex 8 with two equivalents of tritertbutylphenol radical.Finally,the catalytic properties of 1,5 and 8 for the reduction of hydrazine to ammonia at room temperature were investigated with the addition of proton source and reductant.The experimental results show that the catalytic ability of heterobinuclear complexes is significantly better than that of mononuclear precursor complexes,indicating that the synergistic effect of different metal centers in the complexes can promote the hydrazine reduction catalysis.