| Biological enzyme is mild and green catalytic system with great efficiency.Metal-ligand cooperation(MLC)mechanism is a widespread activation mechanism in biological enzymes.Research and development of cheap metal catalysts with MLC reaction activity can provide an important reference for the chemical development of "artificial enzyme",the research on the structure and function of new hydrogen storage materials,and the research and development of cheap and clean substitutes for traditional precious metal catalysts,which has important scientific research significance and application value.Nickel is the second most abundant transition metal in the earth’s crust,and[NiFe]hydrogenase is an important member of the hydrogenase family.Catalysts based on nickel complexes have made remarkable progress in the field of catalytic organic reactions,especially in coupling reactions,but there are relatively few reports on MLC nickel catalysts.In recent years,our research group has devoted itself to the simulation of metalloenzyme activity and developed a series of catalysts with MLC activity,including "Ni-O" cooperative system,which can efficiently catalyze the 1,2hydroboration of nitrogen heterocyclic aromatic compounds.Based on this research,we hope to expand the "Ni-X" cooperative system,explore the similarities and differences between "Ni-N" system and "Ni-O" system in the activation of B-H bond reaction,and expand the application of "Ni-X" cooperative system in the catalytic hydroboration of unsaturated organic compounds.The details are as follows:Ⅰ We designed and synthesized complexes Cp*Ni(Ph2P-NH)(1)and Cp*Ni(Cy2P-O)(2)(Cp*=pentamethylcyclopentadienyl.Ph2P-NH=o-dipenlphosphine phenoxy,Cy2P-O=o-dicyclohexylphosphine phenoxy).and characterized their structures,preliminarily studied their electrochemical properties and redox activity.and investigate the equivalent reactions of complexes 1 and 2 with HBpin and(9BBN)2.The structures of the reaction products[H1Bpin].[H2Bpin],[H1BBN]and[H2BBN]were characterized.The preliminary results show that in the Cp*Ni(PX)complex,the change of the heteroatom X has an obvious effect on the cooperative cleavage of B-bond by "Ni-X".while the steric hindrance and electronic effect of phosphine ligand have little effect on the reaction activity.Ⅱ We studied the activity of complexes 1 and 2 to catalyze hydroboration of ketones,imines and N-heterocyclic aromatic compounds.The experimental results show that complex 2 can efficiently catalyze the borohydrogenation of ketones,imines and N-heterocyclic aromatic compounds.The above experimental results expand the application of "Ni-X" cooperative system in catalytic conversion of organic compounds and provide an important reference for the construction of cheap metal catalytic system based on MLC function. |
