Synthesis And Characterization Of β-diketiminato Lanthanide(Ⅱ) Borohydrides And Phenylene-bridged β-ketoiminate Dilanthanide(Ⅲ) Aryloxides And Their Catalytic Activity

In this thesis three organolanthanide(II) borohydrides stabilized by β-diketiminato ligand were first synthesized and their catalytic behavior for the hydrophosphonylation of aldehydes and unactivated ketones was studied. In addition, the synthesis and reactivity of a series of bimetallic lanthanide aryloxides stabilized by a p-phenylene-bridged bis(β-ketoiminate) ligand were presented, The catalytic addition reaction between carbodiimine and amine and the mechanism were investigated. The main results obtained were described as follows:1. Reaction of anhydrous LnCl3(Ln = Yb, Sm, Eu) with NaL2,6-ipr2(L2,6-ipr2 =[N(2,6-iPr2-C6H4)C(Me)]2CH–) in 1:1 molar ratio afforded the β-diketiminato lanthanide dichlorides. The dichlorides reacted with one equivalent of sodium borohydride and followed by reduction reaction with sodium/ potassium alloy to give the corresponding divalent lanthanide borohydrides. Complexes 1-3 were characterized by X-ray diffraction,IR spectroscopic techniques and elemental analysis. The single crystal structure analysis showed that each central metal in these complexes is ligated by one β-diketiminato, one BH4- group and two THF molecules, and the coordinated geometry around each center metal can be destribed as a distorted trigonal bipyramid.2. The catalytic behavior of these complexes for the hydrophosphonylation of aldehydes and dialkylphosphite were studied. Complexes 1-3 can be used as efficient pre-catalysts for hydrophosphonylation, and the catalytic activity depends on the central metals and the increasing sequence is Sm(2) < Yb(1) < Eu(3). The reaction with complexes L2,6-ipr2YbBH4.2THF(1) and L2,6-ipr2 Eu BH4.2THF(3)in low catalytic loading(0.08 mol%(1),0.05 mol%(3)), gives excellent yields at r.t under solvent free conditions.Complexes(1) and(3) both show a wide range scopy of reactants.3. The catalytic behavior of these complexes for the hydrophosphonylation of unactivated ketones and diethylphosphite were further tested. Complexes 1-3 show the high activity for hydrophosphonylation and a good scope of substrates. The hydrophosphonylation reactions of aromatic ketones and/or hexaheterocyclic ketone with complex(3) afforded the products in the yieldes around 86% to 99% under the conditions of solvent free at r.t in low catalytic loading( 0.08 mol%(3)).4. Reaction of Ln(OAr)3(THF)2(Ar= [2,6-(tBu)2-4-MeC6H2], Ln = Y(4), Nd(5)) with LPhH2(LPh = [OC(Me)CH2C(Me)N-C6H4-NCCH2C(Me)O]) in a 2:1 molar ratio afforded two bimetallic lanthanide(III) aryloxides stabilized by a p-phenylene-bridged bis(β-ketoiminate) ligand, LPh[Y(OAr)2]2(4) 和 LPh[Nd(OAr)2]2(5). Complexes 4 and 5were characterized by spectroscopic techniques, standard analysis and X-ray diffraction.Meanwhile, the known three bimetallic lanthanide aryloxides LPh[Yb(OAr)2]2(6),LPh[Sm(OAr)2]2(7) and LPh[La(OAr)2]2(8) were also synthesized.5. The catalytic behavior of complexes LPh[Ln(OAr)2]2(Y(4), Nd(5), Yb(6), Sm(7), La(8))for the addition of amines to carbodiimides were studied, Complexes 4–8 can be used as efficient pre-catalysts for catalytic addition of amines to carbodiimides, and the ionic radii of the central metals have a significant effect on the catalytic activity with the increasing sequence of La(8) < Nd(5) ~ Sm(7) < Y(4) ~ Yb(6). The catalytic addition reactions with 6 in 0.5 mol% at 60 ℃ under solvent free condition afforded excellent yieds of substituted guanidines and the catalytic system showed a good scope of substrates including primary and secondary amines.6. The catalytic mechanism for the addition reaction of carbodiimides and amines with these complexes were further investigated. A NMR tube reaction with stoichiometric amount of LPh[Y(OAr)2]2(4) and PhNH2 and DIC(diisopropylcarbodiimide)was measured. According to the NMR experimental data the possible catalytic pathway was presented. Firstly, the amination of complex LPh[Y(OAr)2]2(4) by aniline afforded the intermediate LPh[Y(OAr)(NHPh)]2(A). Then, the nucleophilic addition of A to a carbodiimide yielded the guanidino active species LPh[Y(OAr)(iPrNC(NHiPr)NPh)]2(B).The protonolysis of LPh[Y(OAr)(iPrNC(NHiPr)NPh)]2(B) by aniline gave the product guanidine and release LPh[Y(OAr)(NHPh)]2(A) to complete the catalytic cycle.