Synthesis And Characterization Of Bimetallic Lanthanide Complexes And Their Reactivity

A series of lanthanide and lanthanide-zinc heterobimetallic complexes supported bythree kinds of amine-bridged phenolato ligands were synthesized and structurallycharacterized. The catalytic activity of some of these complexes for the polymerizationof L-lactide and D,L-lactide were tested. The p-benzyldiamine-bridged tetra-（phenolate）ligand N,N,N’,N’-tetra-（3,5-di-tert-butyl-2-hydroxybenzyl）-benzene-1,4-diamine,abbreviated as L1H4, The benzylamine-bridged bis（phenolato） ligandPhN{CH₂-（2-O-C₆H₂-But₂-3,5）}₂，abbreviatedas L²H₂, amine-bridged phenolato-alkoxoligand HOCH₂CH₂N{CH₂-（2-O-C6H₂-But2-3,5）}2，abbreviated as L3H3.1. Amine elimination reactions of Ln[N（TMS）₂]₃（μ-Cl）Li（THF）3with L1H4in a2:1molar ratio in THF gave the neutral benzylamine-bridged tetra（phenolate） lanthanideamido complexes L¹[LnN（TMS）₂（THF）]2（Ln=Yb （1）,Y （2）, Sm （3））. The similarreaction of Nd[N（TMS）2]3（μ-Cl）Li（THF）3with L1H4in a2:1molar ratio in toluene gavethe bimetallic lanthanide amide L¹[NdN（TMS）₂（THF）]₂（4）. Complexes1-4werecharacterized by IR, elemental analysis, and NMR spectroscopy in the case ofcomplexes2and3. Structural determination revealed that complexes1-4have asolvated monomeric structure.2. Reaction of AlMe3with L1H4in a2:1molar ratio in THF gave the bimetallicaluminun methyl complex L¹[AlMe]₂（5）. Complex5was characterized by IR, elementalanalysis and single crystal X-ray diffraction.3. Reactions of Ln[N（TMS）₂]₃（μ-Cl）Li（THF）₃with L²H₂in a1:1molar ratio intoluene gave the neutral benzylamine-bridged bis（phenolate） lanthanide amidocomplexes L²LnN（TMS）₂（THF）（Ln=Yb （6）, Sm （7））, and anionicbenzylamine-bridged bis（phenolato） neodymium amide L²Nd[N（TMS）₂]（μ-Cl）Li（THF）（8）. Whereas the similar reaction of Sm[N（TMS）2]3（μ-Cl）Li（THF）3with L²H₂in a1:1molar ratio in THF gave the anionic lanthanide complex L²SmL₂Li（THF）（9）. Complexes6-9were characterized by IR, elemental analysis, NMR spectroscopy in the case ofcomplex6and single crystal X-ray diffraction.4. Reactions of Cp3Ln（THF） with L3H3in a1:1molar ratio in THF at0oC forabout2h, and then at room temperature for about12h, gave the corresponding lanthanide complexes L³₃Ln₃（THF）₂（Ln=Yb （10）, Y （11）） and L³Ln（THF）₂（Ln=Nd（12））. Complexes11and12reacted with Zn（OAc）₂in a1:0.5molar ratio in THF at50oC for about3d, to give the neutral lanthanide-zinc heterobimetallic complexesL³₄Ln₄Zn₂（OAc）₄（Ln=Y （13）） and L³₂Ln₂Zn（OAc）₂（THF）₄（Ln=Nd （15））. Theone-pot reaction of Cp₃Ln（THF） with L³H₃in a1:1molar ratio, and then with Zn（OAc）₂in a1:0.5molar ratio in THF, gave the similar complex L³₂Sm₂Zn（OAc）₂（THF）₄（14）.Complexes10-15were characterized by IR, elemental analysis, NMR spectroscopy inthe case of complex11and13and single crystal X-ray diffraction.5. The reaction of ZnEt2with ligand L3H3in a1:1molar ratio in THF at0oC forabout1h, and then at room temperature for about12h, gave the corresponding zinccomplex L3Zn（THF）（16）. Complex16was characterized by IR, elemental analysis,NMR spectroscopy and single crystal X-ray diffraction.6. The neutral p-benzylamine-bridged tetra（phenolate） lanthanide amido complexesL¹[LnN（TMS）₂（THF）]₂（Ln=Yb （1）,Y （2）, Sm （3）, Nd （4））, and the neutralbenzylamine-bridged bis（phenolate） lanthanide amido complexes L2LnN（TMS）2（THF）（Ln=Yb （6）, Sm （7）） can initiate the ring-opening polymerization of L-lactide andD,L-lactide with high activity, respectively. It was found that the bimetallic rare earthamido complexes1-4showed apparently higher activity than the monometalliclanthanide amido complexes6-7in L-lactide polymerization. These results revealed thatthe bimetallic cooperate effect exists in this system.7. The neutral p-benzylamine-bridged tetra（phenolate） lanthanide amido complexesL¹[LnN（TMS）₂（THF）]₂（Ln=Yb （1）,Y （2）, Sm （3）） can catalyze the guanidine reactionof amine with carbodiimines at room temperature, and the bimetallic yttrium amidocomplex showed the highest catalytic activity.