Rare Earth Metal Complexes:Synthesis,Reactivity And Polymerization Properties

In this thesis,we reported the synthesis of the binuclear half-sandwich scandium aminobenzyl/chloride complex,which showed efficient catalytic activity to afford the triblock copolymers with superior mechanical performances.Whilst,a series of scandium and lanthanum dibenzyl complexes supported by polyaryl-cyclopentadienyl ligands were synthesized and characterized,and their catalytic properties toward styrene polymerization and hydrogenation reaction were studied respectively.In addition,a number of scorpionate supported rare earth metal complexes were synthesized and characterized,and a series of tentative organic transformations were also carried out.The details are listed as follows:1.The binuclear half-sandwich scandium aminobenzyl/chloride complex[(Cp’)Sc(THF)Cl]2[p-(CH2C6H3(o-NMe2)-)2](Cp’=C5Me4SiMe3)(103)was obtained by linking two scandium centers through a bis(amionbenzyl)fragment.When activated with halide abstractor,[(Et3Si)2(μ-H)][B(C6F5)4],complex 103 is capable of copolymerizing styrene and ε-caprolactone to furnish ABA type triblock copolymers(PCL-b-sPS-b-PCL)consisting of perfectly syndiospecific polystyrene(sPS)(B)in the midblock and tunable PCL(A)content in the end blocks.The stress-strain measurements of solution casting film of copolymers demonstrated that the triblock copolymers exhibited superior mechanical performances compared to those diblock BA copolymers(sPS-b-PCL)prepared from mononuclear scandium aminobenzyl/chloride complex[(Cp’)Sc(o-CH2C6H4-NMe2)(THF)Cl]2.A series of half-sandwich scandium dibenzyl complexes have been synthesized by one-pot reaction of potassium derivatives of pentaarylcyclopentadienes(Cp(Ar*)5 or CpAr5)(Ar*=3,5-tBu2-C6H3;Ar=3,5-iPr2-C6H3)or tetra-arylcyclopentadienes(Cp(Ar*)4H,CpAr4H and CpPh4H)with cationic scandium dibenzyl complex[Sc(p-CH2C6H4-Me)2(THF)x][BPh4],generated in-situ from[Sc(p-CH2C6H4-Me)3(THF)2]with[NEt3H][BPh4]in THF.[(CpAr5)Sc(p-CH2C6H4Me)2(THF)](2)bearing pentaarylcyclopentadienyl display two η1-coordinated benzyl ligands without obvious interaction of the ipso-carbon of the phenyl groups.In comparison the two benzyl ligands in[(CpPb4H)Sc(p-CH2C6H4-Me)2(THF)]supported by tetraphenylcyclopentadienyl bond to the scandium center in two different patterns:one is η1-coordination,and the other is η2-coordinate mode.In combination with[Ph3C][B(C6F5)4]and AliBu3,these complexes showed highly active syndiospecific polymerization of styrene,up to 587(kg(sPS)·mol(sc)-1·h-1).The catalytic activity of these complexes decreased with the increasing steric hindrance of Cp ligands around the scandium centre in the order of(CpPh4H>CpAr4H>Cp(Ar*)4H>CPAr5>Cp(Ar*)5H)3.The penta-arylcyclopentadienyl ligands have been widely used as monoanionic ancillary ligands across the Periodic Table.Here,we report that hydrogenolysis of the half-sandwich penta-arylcycopentadienyl-supported lanthanum dibenzyl complex[(CpAr5)La(p-CH2-C6H4-Me)2(THF)](115)(CpAr=C5Ar5,Ar=3,5-iPr2-C6H3)afforded the double-sandwich bimetallic hydrides complexes[(CpAr5)La(μ-H)]2(117).One of five aryl groups in CpAr5 ligand was selectively reduced to planar anionic benzene in complex 117,respectively.Complexes 117 exhibit two pronounced features:the extraordinary upfield-shifted metal hydride resonances and the shortest metal-metal distances.In contrast,hydrogenolysis of the tetra-arylcyclopentylpentadienyl supported lanthanum dibenzyl complex[(Cp(Ar)4H)La(p-CH2-C6H4-Me)2(THF)](118)led to mixtures.4.A series of rare earth metal dialkyl complexes[(TpAd,iPr)Lu(R)2](Ln=Sc,Y,Lu;R=CH2SiMe3,CH2tBu,Me)supported by scorpionate ligand(TpAd,iPr)were synthesized.Hydrogenolysis of[(TpAd,iPr)Lu(CH2SiMe3)2]led to the formation of mononuclear lutetium alkyl/hydride complex[(TpAd,iPr)Lu(H)(CH2SiMe3)](126).The corresponding mononuclear rare earth dihydrido complex remain elusive.In an attempt to synthesize Ln=P(Ph)complexes,it was found that after the first step of the proton reaction,the remaining P-H can’t be abstracted.Under heating conditions in THF,the ligand TpAd,iPr easily decomposed into 3-adamantane-5-isopropylpyrazole(Pz),which afforded tri-pyrazole coordinated rare earth metal complex(Pz)3Lu(THF)2(140).The reaction of TpAd,iPr supported rare earth metal complexes with varied oxygen-Group organic substrates,such as nBu3P=Te,KSCPh3,KOCPh3,HSCPh3,HOCPh3,were also attempted,the expected rare-earth metal oxygen multi-bonded complexes were not isolated.The TpAd,iPr decomposition was also observed in the reaction with nBu3P=Te.