Synthesis Of New Post-transition Metal Carbene Compounds, Application, And Structural Studies

N-heterocyclic carbenes (NHCs) and their transition-metal complexes have attracted significant interest over the past decade in homogeneous catalysis and organometallic chemistry. As ligands on transition metals, NHCs have been found to have properties similar to those of widely employed phosphine ligands. Because of their limited or insignificant toxicity, strong electron-donating properties, higher thermal stability and better stabilizing effects than most of the commonly utilized phosphines, NHCs have become an alternative to the phosphine ligands. In fact, most of the transition metals can afford stable carbene complexes. The dissertation was summarized as follows:1. Picolyl, pyridine, and methyl functionalized N-heterocyclic carbene ligands were synthesized. After deprotonated and reacted with [Cp*IrCl2]2, the functionalized N-heterocyclic carbene half-sandwich iridium complexes were afforded. These complexes have been characterized by 1H-NMR,13C-NMR spectra and elemental analyses. Some of these have also been confirmed by X-ray single-crystal analyses. In the presence of MAO, the complexes containing hemilable ligands were active for the polymerization of norbornene. The obtained poly-norbornenes were characterized by IR,1H-NMR and 13C-NMR and it confirmed that the polymerization is vinyl-addition type. To the best of our knowledge, this is the first report that the iridium carbene complexes catalyze vinyl-addition polymerization of norbornene. After optimized, the pyridine functionalized iridium carbene show moderate activity (1.70×106 g of PNB (mol of Ir)-1h-1). The influence of MAO/Ir ratio and the reaction temperature on the catalytic activities and Mv was also studied. The mechanism of nobornene polymerization reaction is also discussed.2.16-electron metal complexes Cp*M[E2(C2B10H10)] (M= Rh, Ir; E= S, Se) show rich coordination chemistry due to their unsaturation at the metal atom, which has allowed the addition reaction at the metal atom in a dichalcogenolato metal heterocycle. As a strongσ-donor ligand, the NHCs could be added to the electron deficiency half-sandwich starting materials. Complexes containing both NHC and ortho-carborane-1,2-dithiolate ligands can be synthesized by the reaction of Cp*M[E2(C2B10H10)] with NHC ligand in the presence of Ag2O. A different method was found here. This approach was also introduced to trinuclear system. The trinuclear complexes can be obtained from the reaction of Cp*M[S2(C2B10H10)] with silver-NHC complex or from the reaction of dichloride complexes with Li2E2(C2B10H10).3. N-heterocyclic carbene (NHC) silver complexes can be used in pharmaceutical applications, catalysis, transmetalation reactions and etc. In fact, the synthesis of silver NHC complexes is mainly used to transfer to other metal systems because the silver carbene transmetalation method avoids harsh conditions and works efficiently. Silver complexes of NHCs can be prepared from many routes including halogen exchange reactions. It has been proposed that the source of chloride is the solvent which is either 1,2-dichloroethane or dichloromethane. However, after a detailed literature investigation, we found that chlorinated solvents are used for both the synthesis and the recrystallization. We thus question the origin of the halogen exchange reaction. In this part, two silver complexes were synthesized and characterized crystallographically. The presence of chloride in the carbene complex indicates a halogen exchange reaction occurred. The absence of Cl the presence of Br in the other complex shows that the halogen exchange reaction occurred unambiguously during synthesis and not during recrystallization. The silver carbene complex is a good transmetalation agent. It can be used to transfer to [(p-cymene)RuCl2]2(L) and {(p-cymene)Ru[S2(C2B10H10)]}2(L) (L= 1,1'-dimethyl-3,3'-ethylene-di-imidazole-2-ylidene). The latter contains the carbene ligand as well as the 1,2-dicarba-closo-dodecaborane ligand.4. The last two decades have witnessed the tremendous development of coordination-driven self-assembly in supramolecular architectures. Different geometries of metal-containing supramolecular structures are available by variation of the metal complexes and the ligands. As for the cornered metal components, half-sandwich Ir, Rh, and Ru fragments bridged by oxalate or chloranilate subunits have been recently used to synthesize tetra-, hexa-and octanuclear complexes. However, most of the available systems were derived from palladium or platinum species, utilizing diamine or diphosphines derivatives as supporting ligands. As a replacement of the phosphine ligands, we assumed that the NHCs not only can be developed as catalysts but also can be used in the supramolecular chemistry. NHCs have only been explored in metal-directed self-assembly chemistry recently. The rigid bis-carbene ligand was used as building spacer in the construction of a molecular rectangle. However, to the best of our knowledge, NHCs has never been used as the "corner" ligands to form metallamacrocycles. Herein, we present some new complexes [(MesC-Cmeth)Pd(LL)]2(OTf)4 (MesC-Cmeth= 1,1'-dimesityl-3,3'-methylene-diimidazolin-2,2'-diylidene; LL= 4,4'-dithiodipyridine, 1,2-bis(4-pyridylthio)ethane, 1,3-bis(4-pyridylthio)propane) featuring bidentate chelating NHC palladium complex as the corner element and pyridine-based flexible ligands as the bridging units.5. The [(PPh2)2(C2B10H10)] ligand, one of the 1,2-diphosphino carborane derivatives, is of particular interest because it is structurally analogous to the cis-forms of ethyl enediamines, ethylenediphosphines, bis(diphenylphosphino) ferrocene and etc, which have been widely used in the coordination-driven self-assembly chemistry. In this part, [MCl2{(PPh2)2(C2B10H10)}] (M= Ni, Pd) were used to react with AgOTf. It was found that the reactivity of these complexes is different. The reaction of the palladium complex [PdCl2{(PPh2)2(C2B10H10)}] with AgOTf affords a binuclear nido-carborane complex [Pd2(μ-OTf)2{(PPh2)2(C2B9H10)}2] in high yields, however, the reaction of analogous nickel complex [NiCl2{(PPh2)2(C2B10H10)}] with AgOTf leads to the formation of a heteronuclear complex [Ni{(PPh2)2(C2B9H10)}](μ-Cl)2[Ag{(PPh2)2(C2B10H10)}] and a homonuclear complex [Ag2(μ-Cl)2{(PPh2)2(C2B10H10)}2]. The presence of Ag in the products indicates there is a Ag intermediate in the reaction. The Ag intermediate [Ag2(μ-OTf)2{(PPh2)2(C2B10H10)}2] was readily obtained by the reaction of [(PPh2)2(C2B10H10)] with AgOTf in high yields. The intermediate was also used to react with [NiCl2{(PPh2)2(C2B10H10)}] to give [Ni{(PPh2)2(C2B9H10)}] (μ-Cl)2[Ag{(PPh2)2(C2B10H10)}] in high yields, while it reacts with [PdCl2{(PPh2)2 (C2B10H10)}] to produce [Pd2(μ-Cl)2{(PPh2)2(C2B9H10)}2], [Pd{(PPh2)2(C2B9H10)}2] and [Ag2(μ-Cl)2{(PPh2)2(C2B10H10)}2].