Reactions Of ?-diimine Supported Low-valent Aluminum And Gallium Compounds With Carbodiimide

The chemistry of low-coordinate main-group metal ions in the unusual low oxidation states has attracted much attention in recent years.These species have attracted great interest not only because of the novel bonding nature of the low-valent,low-coordinate metal centers,but also because they display fascinating reactivity toward a variety of small molecules as well as potential applications in catalysis,which is similar with transition metal.While,these unusual valence main-group metals are extremely sensitive to water and oxygen and difficult to obtain under normal conditions.The key to the formation of low-coordinate metal ions in the unusual low oxidation states is the need for appropriate steric hindrance of the ligand to stabilize.?-diimine ligand can be easily oxidized or reduced by one or more electrons and can be readily modified by the variation of both the ligand backbone and substituents at the nitrogen.Explore the reaction of Group IIIA low-valent Al and Ga compounds with small molecules to achieve gain and loss of electrons similar to transition metals and participate in small molecule activation reactions.This thesis consists of four parts:1. Summarized the development of Group IIIA of low-valent Al and Ga metal-metal or multiple bonds synthesis,structure and applications in activating small molecules and catalysis of several representative compounds.2. The reactions of the low valent dialumane with different carbodiimide substrates RN=C=NR?R=Cy,iPr,dipp and 2,6-i-Pr-C₆H₃?were investigated,which undergo particularly diverse processes,including insertion,unusual[2+4]cycloaddition,C-H activation,and a hydrogen transfer process.Reaction with one equivalent of dicyclohexylcarbodiimide?DCC?yields the intercalation compound[LAl?CyNCNCy?Al?THF?L]?2?;with two equivalents of diisopropylcarbodiimide?DIC?reaction to obtain an asymmetric insertion[2+4]cycloaddition product[LAl?iPr N=C-NiPr?Al?iPr N-C=NiPr?L]?3?;compound 2 reacted with an equivalent of DCC A similar[2+4]cycloaddition intermediate was obtained,but the intermediate was unstable and obtained[LAl?CyNCNCy?Al L^-H?CyNCNHCy?]?4?by activation of the intramolecular C-H bond and[1,7]hydrogen migration.After the compound 4 is further reduced with Na,the compound N of the CyNCNHCy fragment on the compound 4 loses H atom[LAl?CyNCNCy?Al L^-H?CyNCNCy?]Na?THF?₂?5?.In the reaction with the higher steric hindered substituent carbodiimide?Dipp;t Bu?,mononuclear metal compounds [LAl?ArNCHNAr?Al]?6?and[LAl{tBuN?C??H?Nt Bu}]?7?.3. The?-diimine ligand stabilizes low-valence gallium carbene compounds[?dpp-dad? Ga Na?THF?₄]1b;[?dpp-dad?Ga K?THF?4?dpp-dad?][K?THF?₆]1c reacts with sterically hindered carbodiimide RN=C=NR?R=iPr,Cy??DIC;DCC?,obtain high-efficiency C-N coupling compound[LGa N?R?C?RN?N?R?C?RN?][Na?THF?₃]?R=iPr,8;Cy,9?and[LGa N?Cy?C?CyN?N?Cy?C?CyN?][K?THF?₄]?10?.At same time,reacted with a larger steric hindrance Ar-N=C=N-Ar?Ar=2,6-iPr C₆H₃?to obtain compound[LGa?2,6-iPr₂C₆H₃N?₂C][Na?THF?₂]?11?.4. Further reduction of Compound 1 and the reaction of bis?trimethylsilyl? carbodiimide to obtain the addition product[[LAl{?N?CNSi Me₃}{?Si?Me₃}][Na?thf?₃]?12?,with DIC in different solvents afforded C-C coupling product[LAl??-C₂N₄iPr₄?.Na?THF?]₂?13?and[??DME?Na??-C₂N₄iPr₄?Al???-ArNC?CH₂?=CMeNAr?]₂?14?.