Synthesis Of Thiolate-Bridged Cobalt-Ruthenium Complexes And Their Reactivity Toward Dinitrogen Fixation

Based on the construction of thiolate-bridged heterobimetallic complexes,a series of novel thiolate-bridged cobalt-ruthenium heteronuclear complexes were synthesized through the rational modulation of auxiliary ligands in this dissertation.Meanwhile,their reactivity toward dinitrogen fixation was well studied.On this basis,further investigation indicated that these heterobimetallic complexes all can serve as good catalysts for the reductive silylation of N₂.Firstly,a novel thiolate-bridged cobalt-ruthenium heteronuclear complex[Cp*Co（μ-1κ³SSS′:2κ²SS-tpdt）RuCl₂（PPh₃）₂]（1,Cp*=η⁵-C₅Me₅,tpdt=S（CH₂CH₂S^-）₂）was synthesized through the self-assembly reaction of mononuclear complexes[Cp*Co（η³-tpdt）]and[RuCl₂（PPh₃）₃].Subsequently,a coordinately unsaturated thiolate-bridged cobalt-ruthenium complex[Cp*Co（μ-1κ³SSS′:2κ²SS-tpdt）RuCl（PPh₃）₂][BPh₄]（2）was generated through the reaction of complex 1 and dehalogenation agent Na BPh₄.However,due to the strong trans influence and electronic effect of auxiliary ligand,complex 2 failed to realize the coordination activation of dinitrogen.Subsequently,a thiolate-bridged cobalt-ruthenium complex[Cp*Co（μ-1κ³SSS′:2κ²SS-tpdt）RuCl₂（dppe）]（3）with 1,2-bis（diphenylphosphino）-ethane（dppe）ligand was synthesized by modulation of the auxiliary phosphine ligand through same synthetic method.Ulike 1,treatment of complex 3 with Na BPh₄ can realize the coordination activation of dinitrogen.The first example of cobalt-ruthenium N₂ complex[Cp*Co（μ-1κ³SSS′:2κ²SS-tpdt）RuCl（N₂）（dppe）][BPh₄]（4）was successfully isolated and characterized.The X-ray crystallographic and infrared spectroscopy analysis revealed that the ligated N₂ adopted a terminal coordination fashion.One step further,the in situ variable-temperature ¹H NMR spectroscopic studies revealed that N₂ can realize the reversibly coordination and dissociation at the ruthenium center.When the temperature rises,dinitrogen dissociates from the ruthenium center to form coordinately unsaturated complex[Cp*Co（μ-1κ³SSS′:2κ²SS-tpdt）RuCl（dppe）][BPh₄]（5）with the rotation of bidentate dppe ligand.Dinitrogen re-coordinates and reaches dynamic balance when the temperature decreases.On the basis of dinitrogen coordination activation,the catalytic performances of these heteronuclear complexes were explored.The results show that these complexes can catalyze nitrogen reductive silylation under ambient temperature and pressure.