Synthesis And Reactivity Of Zinc Hydrides Based On A New Type Of Phosphorus-containing Tridentate ?-diketiminato Ligand

The dissertation focuses on studying the synthesis and reactivity of a new type of phosphine-containing ?-diketiminato ligand zinc hydrides.1.Synthesis of zinc hydrides.We designed a new type of ?-diketiminato ligand precursor bearing a pendant phosphine group.Metalation of ligand precursors with ZnEt2 gave zinc monoalkyl complexes,which reacted with an equimolar amount of 2,6-diisopropylphenol to give zinc aryloxide complexes with the liberation of ethane.Finally,the target zinc hydrides were obtained through the metathesis reactions of with PhSiH3 under mild conditions.2.Reactivity of zinc hydrides.(1)Addition reaction occurs between unsaturated small molecules and zinc hydrides.Zinc hydrides reacted with chalcone to afford 1,4-addition products.However,they were readily converted into zinc formats upon the addition of CO2(1.0 atm)at room temperature.(2)Transition metal-induced dehydrogenative homocoupling of zinc(?)hydrides to Zn(?)-Zn(?)bonded complexes were developed.When zinc hydrides with the widely used zero-valent Pd(PPh3)4 or Pt(PPh3)4 in a 2:1 reductive elimination of H2 occurred and gave zinc-zinc bonded complexes.The reactions between zinc hydrides with zero-valent nickel reagent Ni(COD)2(COD:1,5-cyclooctadiene)were also performed in a 2:1 molar ratio.The reactions gave heterotrimetallic hydride-bridged[Zn-Ni-Zn]complexes.DFT computation study indicated that an oxidative addition/reductive elimination process at the palladium center might be responsible for the formation of a covalent Zn-Zn bond.Further reactions of hydride-bridged complexes[Zn-Ni-Zn]with CO or isonitrile resulted in the reductive elimination of H2 and the formation of low-valent unsupported Zn(?)-Zn(?)bonded complexes.(3)The reactions between zinc hydrides and transition metals in a 1:1 ratio gave bimetallic complexes.When zinc hydrides were mixed with[(r)5-C5H4Me)Mn(CO)3]or Cr(CO)6,hetetotrimetallic hydride-bridged complexes were produced.However,the addition of Co2(CO)8 reagent on zinc hydrides resulted in the release of H2 and the formation of complexes by the reductive elimination.