Steric Effect On Synthesis And Reaction Behavior Of β-Diketiminato Organolanthanide

Based on theβ-diketoimide ligand,24 organolanthanide complexes were synthesized in this thesis. Among them,23 complexes were characterized by X-ray single crystal diffraction. Furthermore, catalytic behavior of some complexes for the polymerization of caprolactone/lactide and guanidine-forming reaction between amine and carbodiimine were studied. Sterically induced effect on the syntheses and reaction behavior of lanthanideβ-diketoimides were detected as well. The main contents were listed below.1. Reaction of anhydrous LnCl3 with Na(o-Me-C6H4NC(Me)CHC(Me)NC6H4-o-Me) in 1:3 molar ratio afforded homoleptic tris(β-diketoimide) lanthanide complexes: LnL32-Me (Ln= Yb (1), Sm (2), Nd (3), Pr (4), La (5), Eu (6)) and YbL34-Me (7). These complexes were characterized by elemental analysis, IR, NMR and X-ray diffraction. Single crystal structure analysis showed that these complexes are monomeric. The coordination number of metal center is 6. The coordination geometry around the metal center can be described as distorted octahedron. Six coordinated N atoms were all from threeβ-diketoimides.2. Reactions of number of anhydrous LnCl3 with Na(2,6-(Me)2-C6H4NC(Me)CHC-(Me)NC6H4-2,6-(Me)2) in 1:3 molar ratio afforded four lanthanide complexes, NdL2,6-MeL2,6-Medep·THF (8),SmL2,6-MeL2,6-Medep·THF (9), ErL2,6-MeL2,6-Medep·THF (10), YbL2,6-MeL2,6-Medep' (11).Deprotonation of ligands in the reaction were observed. With the difference of ion radius of lanthanide, the coordination mode of deprotonatedβ-diketoimide ligand to metal center varied at the same time. In complexes 8,9 and 10, a five-member ring was formed, respectively. Otherwise, in complex 11, a Yb-CH2 bond formation was occurred.3. Reaction of anhydrous EuCl3 with Na(2,6-(Me)2-C6H4NC(Me)CHC(Me)NC6H4- 2,6-(Me)2) in 1:3 molar ratio afforded two unexpected products EuL2,6-Me2?THF (12) and [{N(2,6-Me2C6H3)C(Me)}2CH]2 (13). We suppose the sterically induced reduction (SIR) lead to the formation of 12, and it is first observed in the synthesis of non-cyclopentadienyl lanthanide complex. It is interesting that above reaction also lead to the occurance of oxidative coupling between twoβ-diketoimide ligands.4. Reactions of anhydrous LnCl3 with Na(2,6-iPr2-C6H3-NC(Me)CHC(Me)N-C6H5) in 1:2 molar ratio produced threeβ-diketoimide-ligand-based lanthanide chlorides YbLph2,6-ipr2Cl (15), YLph2,6-iprCl (16) and SmLPh2,6-Pr2Cl. Corresponding heterolepticβ-diketoimide-igand-based lanthanide chloride YbL2-MeL4-Cl-THF (14) can be generated by a tandem reaction of anhydrous YbCl3 with Li(o-Me-C6H4NC(Me)CHC(Me)NC6H4-o-Me) and Li(p-Cl-C6H4NC(Me)CHC-(Me)NC6H4-p-Cl) in 1:1 molar ratio, respectively. Complexes 14,15,16 were characterized detailed as follows,14,15 and 16 by elemental analysis,15 and 16 by IR,14 and 15 by X-ray diffraction,16 by1H NMR.5. Functionalization of 15,16, SmLph2Cl with NaNH(C6H3-2,6-iPr2) in 1:1 molar ratio, respectively led to the formation of three lanthanide amides YbLPh2,6-iPr2NH(C6H3-2,6-iPr2) (17), YLph2,6-iPr2NH(C6H3-2,6-iPr2) (18), SmLph2,6-iPr2NH(C6H3-2,6-iPr2) (19). All the complexes were determined by EA, IR and X-ray diffraction. Single crystal structure analysis showed that these complexes are monomeric without solvent coordination. The coordination number of metal center is 5. The coordinative geometry around the metal center can be described as distorted bipyrimidal. Five coordinated N atoms were from twoβ-diketoimide ligands and one amino ligand. But the reaction of 15 with 2,6-tBu2-4-MeC6H2ONa in 1:1 molar ratio afforded a ytterbium dichloride YbLph2,6-iPr(OC6H2-4-CH3-2,6-tBu2)2(21).6. The influence of steric hindrance effect on the catalytic behavior of P-diketoimide-ligand-based lanthanide complexes was examined. It was found that in the ring-opening polymerization of s-caprolactone (L-lactide). and guanidine-forming reaction, increased steric hindrance ofβ-diketoiminato ligand lead to higher catalytic activity of corresponding homoleptic lanthanide complexes. It has been demonstrated obviously in the ytterbium-catalysis, YbLH3 and YbL4-Me3 showed lower reactivity, otherwise YbL2-Me3 showed higher reactivity.7. Catalytic reactivity of complexes 8,17,18 and 19 for the ring-opening polymerization of s-caprolactone and L4actide were detected. All the complexes except 18 can efficiently initiate the polymerization to afford the molecular weight-controlled polymer. (Reaction of complex 11 with 4-tBUC6H4OH in 1:0.94 molar ratio at 50℃afforded bis(aryloxo) lanthanide complex YbL2,6-Me(OC6H4-tBu)2-2THF (20).8. Study of reaction of homolepticβ-diketoimide lanthanide complexes with CO2, cyanide, isocyanide, carbodiimine and Na/K alloy were also carried out. It regretted that no obvious evidence account for the final products had been obtained.