Synthesis,Structure And Reactivity Studies Of Organonickel And Organomagnesium Complexes

In recent decades,organometallic chemistry has made rapid development,and various novel organometallic compounds have been synthesized.Since 1980s,the focus of organometallic chemistry is gradually shifting from synthesis to application,especially the low-valent polynuclear organometallic compounds containing many low-valent active centers.Their application in small molecule activation and catalysis has gradually attracted people's attention.The large aggregation of studies indicated the appropriate ligands play a very important role to stabilize the low-valent metal compounds.The coordination between ligands and metals will reduce the valence electron orbit of metal atoms,and increase the valence state of metals.Therefore,it is necessary to reduce the ligancy of as few as possible in order to make the valence electrons on the central metal can be filled in the bonding orbit as the largest so that the low-valent metal compounds can be obtained.At the same time,ligand with the low steric hindrance will lead to intramolecular reactions to generate metal clusters or polymers.However,the high steric hindrance will hinder the nucleophile to coordinate with metal center so that the activity of metal center would be reduced.The properties of ligands play an important role in the regulation of catalyst activity and stereoselectivity.Therefore,the design and synthesis of ligands has become a challenge for organometallic chemists.Diimine as a bidentate nitrogen-containing ligand,has variable steric hindrance and controllable valence state,which can effectively stabilize low-valent metal compounds.The ligand can not only obtain an electron,form a paramagnetic negative monovalent radical state,but also further obtain an electron,form diamagnetic negative divalent enediamine.Due to the abundant electronic configuration of these ligands,a variety of possible electronic configuration complexes are formed together with metal centers with variable valence states,which show interesting structures,properties and functions,and have good performance in magnetic materials and catalysis.1.In this thesis,we utilized the Ni?Ni bonded compound[{Ni(?-L^{i Pr-2,6})}₂](L^2,6-iPr=[?2,6-ⁱPr-C₆H₃?NC?Me?]₂)?1?,which is supported by?-diimide,and investigated its reactivity with small unsaturated molecules such as nitriles,alkynes and isocyanates.The products of[L^{2,6-i Pr} Ni??²-N?C?CH₃?₃?]?2?with?² coordination and[L^2,6-iPrNi{[(N?CSi?CH₃?₃]₂}]?3?terminal coordination between Ni and nitriles were obtained when nitriles are used as substrates.Meanwhile a dinickel[Ni₂L₂^2,6-iPr??-CH?CCO₂Et?]?4?and a nomonickel[L²,6-iPr,6-iPr Ni??²-CH?CPh?]?5?were obtained when alkyens were used.When the small molecule was isocyanate,the products[L^2,6-iPr Ni??²-O=C=N?CH₃?₃?]?6?,[L^2,6-iPrNi??²-O=C=N?1-Admantyl??]?7?and[L^2,6-iPrNi(?²-O=C=NPh?p-OMe?]?8?were obtained.However,the yield of product 8 was very low.After the separation and purification of the product,we got the product of[?p-OMe?₃?NH?₂N?CO?₂].When the substituent of isocyanate was p-fluorobenzene,a similar product[?p-F-Ph?₃?NH?₂N?CO?₂]?9?was obtained;while when the substituent of isocyanate was benzyl,a cyclotrimer compound[?PhCH₂NCO?]₃?11?was obtained.Compounds 2-11 were characterized by single crystal diffraction,nuclear magnetic resonance or electron paramagnetic resonance,infrared spectroscopy and DFT calculation.2.In addition,by adjusting the steric hindrance of the ligands,we changed from the[?2,4-iPr₂-C₆H₃?NC?Me?]₂ to[?2,4-Me₂-C₆H₃^?NC?Me?]₂,and successfully synthesized a compound[(L^2,4-Me)₃Ni₃Br₆]?12?containing trinuclear nickel.In this compound,Ni is+2valence,and further reduced to trinuclear Ni?0?compound[{Ni(?-L^Me-2,4)}₃]?13?by sodium.And compound 13 can catalyze the[2+2+2]cyclotrimerization of alkynes.And the substrates universality and catalytic reaction kinetics were studied.Due to the excellent solubility of compound 13 in n-hexane,the catalytic reaction can be carried out in non-polar solvent,and the greater difference of solubility of 1,2,4-benzene derivatives and 1,3,5-benzene derivatives formed by some substrates in n-hexane improves the regioselectivity of the reaction.And the crystal structures and electronic configuration of 12 and 13 were studied by X-ray crystallography,density functional theory?DFT?and nuclear magnetic spectroscopy(¹H NMR,¹³C NMR).3.Pillar[n]arenes are a new kind of main macrocyclic molecules after crown ethers,cyclodextrins,calixarenes and cucurbit[n]uril.Their rigid column structures and?-electron rich cavity are conducive to the assembly of different types of guests.We used pillar[n]arenes?P5A?to encapsulate Grignard reagents,upon treatment of RMgX?R=Me,nBu,n-pentyl,n-heptyl and n-octyl;X=Cl,Br,I?with P5A,a series of host-guest complexes have been isolated,including six dinuclear alkyl?halide?magnesium species with different alkyl/halide ratios,?P5A?_n[?THF?RMg??-R?_x??-X?_2-xMgR?THF?]?complexes 17-22 with R=Me,nBu,n-pentyl,n-heptyl,n=1 or 2?and one mononuclear complex?P5A?[Mg?n-octyl?Br?THF?₂]?23?.Notably,for the shorter alkyls,i.e.,Me,n-Bu,and n-pentyl,a dimeric compound with terminal alkyl groups and R/X bridges is encapsulated between two P5A macrocycles through the coordinated THF molecules.In contrast,the longer homologues n-heptyl and n-octyl?in complexes 22 and 23?can enter to the cavity of P5A.The crystal structures and solution properties of these complexes were studied by X-ray crystallography and nuclear magnetic spectroscopy(¹H NMR and ¹³C NMR).The host P5A with linear alkylmagnesium host-guest complexes were synthesized,which made Grignard reagents were solidified.In addition,and the reactivity of the host-guest complex 23 of n-octyl magnesium bromide was studied.The study of reaction activity shows that the host-guest complex 23 retains the reaction activity of Grignard reagent,and due to the interaction between alkyl chain and P5A,the product 1-phenylnonan-1-ol producing by the reaction of complex 23 and benzaldehyde can form host-guest complex with P5A and crystallize from organic solvent.Therefore,it is convenient for the purification of the product.