Studies On Synthesis, Structures And Properties Of Half-Sandwich Iridium And Rhodium Complexes

The half-sandwich complexes[Cp^*M(μ-Cl)Cl]₂(Cp^*=η⁵-pentamethyl-cyclopentadienyl, M=Ir,Rh)have been widely used organometallic compounds,and occupied very important position in organometallic chemistry.The half-sandwich iridium and rhodium complexes have attracted considerable attention in academic fields over the past decade.And the structures and properties studies of functional half-sandwich complexes are concerned by chemists,and the corresponding reports are update everyday.This thesis is focused on the half-sandwich complexes.1.The bidentate and tridentate organochalcogen(S,Se)compounds can be easily prepared in one step via the reactions of methylene,ethylene or prydine based bridged methylimidazolium dibromide with sulfur or selenium powder in the presence of K₂CO₃ in MeOH solution in moderate yields.Reactions of[Cp^*Ir(μ-Cl)Cl]₂ and [Cp^*Rh(μ-Cl)Cl]₂ with bidentate organochalcogen(S,Se)ligands and tridentate pyridyl-based SNS-pincer ligands result in the formation of the 18-electrons half-sandwich complexes,respectively.In these half-sandwich complexes molecular structures,the sulfur or selenium and nitrogen atoms coordinated with centre metal. There is a eight-or nine-membered rings in 18-electrons half-sandwich complexes, respectively.All compounds have been characterized by elemental analysis,NMR and IR spectra.The ligands such as[S₂]or[Se₂]compounds were introduced in Cp^* system may change the complexes structures and chemical properties.After activation with methylaluminoxane(MAO),the half-sandwich iridium complexes with organochalcogen ligands exhibit moderate activities for the vinyl polymerization of norbornene.And the reactions of[Cp^*M(μ-Cl)Cl]₂(M=Ir,Rh)with anionic tripodal ligand tris(2-mercapto-1-methylimidazolyl)borate([Tm^Me]K)lead to formation of the 18-electron complexes.Each center metal is coordinated by three sulfur atoms from one ligand and containing three eight-membered macrocyclic rings.The geometry around every metal center is described as a three-legged piano-stool,which is common in half-sandwich complexes.There is no any interaction between B atom and metal atom.2.A series of 18-electrons binuclear half-sandwich iridium(â…¢)and rhodium(â…¢) complexes containing both dichalcogenolate carborane or carbonate and N-heterocyclic carbene(NHC)ligands have been synthesized through two different routes.And the used starting materials are 16-electrons half-sandwich complexes [Cp^*M{E₂C₂(B₁₀H₁₀)}]or Cp^*M(μ-O)₂CO(E=S,Se;M=Ir,Rh),respectively.In addition,the molecular structures of 18-electrons binuclear half-sandwich complexes have been determined by X-ray crystallography.And the reactions of [Cp^*M(μ-Cl)Cl]₂ and[(p-Cymene)RuCl₂]₂ with disodium maleonitriledithiolate (Na₂Mnt)yield the 16-electron complexes Cp^*Ir(Mnt)and[(p-Cymene)Ru(Mnt)], which can further react with PPh₃ to form the corresponding 18-electron half-sandwich complexes.3.When[Cp^*Ir(μ-Cl)Cl]₂ was treated with five potentially multifunctional ligands tetradentate N₂O₂ donors:2,5-diarylamino-1,4-benzoquinone derivatives (CeX₂O₂N₂R₂;X=H,or Cl)in the presence of excess NEt₃ at room temperature,the purple half-sandwich binuclear Ir complexes were isolated in moderate yields, respectively.In molecular structures,each iridium atom can be described as a three-legged piano-stool,and the iridium atom was coordinated by O and N atoms of ligand and one Cl atom.Treatments of binuclear half-sandwich iridium complexes with bidentate ligands(L)such as pyrazine,4,4'-bipyridine(bpy)in the presence of Ag(OTf)in CH₃OH solution gave the corresponding tetranuclear complexes, respectively.The molecular structures of above results have been determined by single-crystal X-ray analysis.There is noÏ€-Ï€interactions between independent molecules,and the molecular stacking can not form rectangle channels due to the bulky asymmetry structure of tetradentate N₂O₂ donors. 4.The four mononuclear Ni(â…¡)complexes were obtained by the reactions of Ni(PPh₃)₂Br₂ with organochalcogen(S,Se)ligands,respectively.And the crystal structures of Ni(â…¡)complexes are determined by X-ray crystallography.The local geometry around the nickel atom in complexes were distorted tetrahedron with coordinate S(Se)and two Br atoms,and the organochalcogen ligands form an eight or a nine-membered rings with the nickel atom included.After activation with methylaluminoxane(MAO),the nickel complexes exhibit high activities for addition-polymerization of norbornene(1.42×10⁸ gPNBmol^-1Nih^-1)with viscosity-average molecular weight(M_v)of the polymer is 10⁶ gmol^-1.The effects of the Al/Ni ratio,reaction temperature and reaction time to norbornene polymerization are also investigated.The microstructure of the obtained polynorbornene is characterized by NMR and IR spectra.The results show the polymer is typical of vinyl-type products.All polynorbornenes are soluble at room temperature in chlorobenzene and o-dichlorobenzene solvents,and show well thermal stability.