Synthesis And Characterization Of Metal Complexes With Macrocyclic Tetra(N-Heterocyclic Carbene)Ligands

In recent years,polydentate macrocyclic N-heterocyclic carbene ligands have attracted researchers' attention due to their unique coordination behaviours.At present,many macrocyclic NHC complexes of varied metals have been synthesized,some of which exhibit catalytic and luminescence properties.However,the types of macrocyclic ligands are still limited,especially the tetradentate and polydentate macrocycles with benzimidazolidene as NHC units have been rarely reported.The main contents of this dissertation are focused on the synthesis,characterization and properties of macrocyclic NHC-Ag(I),Au(I),Ni(II),Pd(II)complexes,which includes the following three aspects:1.Synthesis,characterization and properties of silver(I)and gold(I)complexes with tetra-carbene macrocyclic ligandsFive Ag(1)and Au(I)complexes with macrocyclic tetradentate N-heterocyclic carbene(NHC)ligands have been prepared via the reactions between three macrocyclic tetrabenzimidazolium salts with metal precursors.Three different structures,including a trinuclear one containing a NHC-Ag-(H2O)moiety and a hexanuclear propeller-like supramolecular assembly,are found for the Ag-NHC complexes([Ag2(L1)](PF6)2(1),[Ag3(L2)(H20)2](PF6)3(2),[Ag6(L3)3](PF6)6(3)).Binuclear Ag(I)and Au(I)complexes 1,4 and 5 exhibit photoluminescence.2.Synthesis and characterization of nickel(?),palladium(?),platinum(?)and cobalt(?)complexes with tetra-carbene macrocyclic ligandsTwelve Ni(?),Pd(?),Pt(?)and Co(?)complexes([Ni(L')](PF6)2(6),[Ni(L2)](PF6)2(7),[Ni(L3)](PF6)2(8),[Pd(L1)](PF6)2(9),[Pd(L2)](PF6)2(10),[Pd(L3)](PF6)2(11),[Pt(L1)](PF6)2(12),[Pt(L2)](PF6)2(13),[Pt(L3)](PF6)2(14),[Co(L')](PF6)2(15),[Co(L2)](PF6)2(16)and[Co(L3)](PF6)2(17))with macrocyclic tetradentate N-heterocyclic carbene(NHC)ligands have been prepared via the reactions between three macrocyclic tetrabenzimidazolium salts with metal precursors.The Co(II)complexes show tetrahedral configuration and Ni(II),Pd(II)and Pt(II)complexes adopt square-planar geometry,in which the different ring-size of the macrocyclic tetracarbene ligands lead to the variation of metal-carbene bond lengths.The ?-? stackings are observed between the rigid aromatic benzimidazole rings in the nickel group complexes.3.Synthesis,structure and catalytic properties of dinuclear iridium(I)complexes with a hexadentate macrocyclic diamine-tetracarbene ligandTwo dinuclear macrocyclic Ir(I)-NHC complexes[Ir2(L4)(COD)2](PF6)2(18)and[Ir2(L4)(COD)Cl]Cl(19)have been prepared from the reaction between[Ir(COD)Cl]2 and a hexadentate macrocyclic N-heterocyclic carbene(NHC)ligand precursor(H4L4)(PF6)4 containing four benzimidazolium and two secondary amine groups.Furthermore,18 and 19 were carbonylated into[Ir2(L4)(CO)4](PF6)2(20)and[Ir2(L1)(CO)2Cl]Cl(21),respectively.Notably,18 can capture the chloride ion to turn itself into 19 accompanying with the transformation from cis-to trans-configuration due to the flexibility of macrocyclic ligand.19 is unusual with a Ir(I)centre exhibiting a distorted tetragonal pyramid geometry since such five-coordination is rarely reported for Ir(I)-NHC complexes.The catalytic properties of 18,19 and a related mononuclear Ir(I)complex[Ir(L5)(COD)](PF6)(22,L5 = bis-NHC ligand)have been evaluated in 1,4 conjugate addition reactions of aryl boronic acids to cyclohexen-2-one.These three complexes are the first examples of Ir(I)-NHC species showing such catalytic properties for 1,4-addition reaction,which possess higher catalytic activities than the reported Ir(I)complexes.