Synthesis And Reactivity Of Magnesium Complexes Based On Tridentate Phosphine-containing ?-diketiminato Ligands

The dissertation presents the synthesis,structure and reactivity of magnesium compounds supported by phosphine-functionalised ?-diketiminato ligands.1.Synthesis of magnesium alkyl compounds.We designed a new type of ?-diketiminato ligand precursor bearing a pendant phosphine group.Metalation of ligand precursors with nBu2Mg?Cy2Mg and tBu2Mg gave magnesium alkyl complexes with the release of alkane.Meanwhile,the salt elimination reaction between the lithium salt of the ligand and the benzyl magnesium chloride produces the magnesium benzyl compound.2.The reactions between magnesium alkyl complexes and transition metals.(1)We firstly found that transition metal was able to induce ?-H elimination of magnesium alkyl complexes to produce heterotrimetallic hydride-bridged Mg-Ni-Mg complexes with the shortest Mg-Ni bonds.The reactions between magnesium alkyls and zero-valent nickel reagent Ni(COD)2(COD=1,5-cyclooctadiene)were performed in a 2:1 molar ratio,which gave heterotrimetallic hydride-bridged[Mg-Ni-Mg]complexes 5a.We also isolated and characterized the hydride-bridged[Mg-Ni]intermediate 6a,and performed DFT theoretical calculations on its bonding mode,confirming that the Mg-H-Ni part has a three-center two-electron structure.The mechanism for the formation of these compounds was initially expored by in-situ NMR spectroscopy.In addition,we have proposed three possible mechanisms through DFT theoretical calculations.(2)The magnesium alkyl complex la and other group ? transition metal reagent[(?3-C3H5)PdCl]2 was performed in a 2:1 molar ratio to obtain a quad-core multimetallic compound 7 with a cage structure.3.The reactivity of magnesium-nickel polymetallic compounds.(1)The reactivity of the hydride-bridged[Mg-Ni-Mg]complex 5a was studied in detail.Compound 5a has a unique reactivity and can undergo coordination reaction with isonitrile,Mg-H bond insertion reaction with carbodiimide,and dehydrogenation reaction with phenylacetylene to form a series of new multimetallic complexes.(2)When fluorobenzene was chosen as solvent,the outcome was different from that of the above experimentals.The reactions between magnesium alkyls and Ni(COD)2 were performed in a 2:1 molar ratio in fluorobenzene,the nickel and magnesium center synergistically activated C-F bond of fluorobenzene to obtain two fluorine-bridged complexes 11 and 12.