Study On The Catalytic Behavior Of Lanthanide/Sodium Heterobimetallic Clusters And Complexes

Five lanthanide/sodium alkoxide heterobimetallic clusters, three anionic aryloxide complexes and four aryloxide complexes were synthesized in high yield with -OCH₂CH₂NMe₂ and -OAr as ligand, respectively. The catalytic activity of lanthanide/sodium heterobimetallic alkoxide clusters for polymerization of MMA and acrylonitrile and amidation of aldehydes with amines were examined. The catalytic activity of anionic aryloxide complexes for amidation of aldehydes with amines and the catalytic activity of aryloxide complexes for guanylation of amines with carbodiimide were tested. The main results obtained are as follows:1. Reaction of sodium alkoxide NaOCH₂CH₂NMe₂ with LnCl3 in 6:1 molar ratio in the presence of one equiv of NaOH gave the alkoxide clusters Ln2Na8(OCH₂CH₂NMe₂)12(OH)2 (Ln = Pr 1; Nd 2; Sm 3; Yb 4; Y 5). Single crystal X-ray analyses for 1 and 5 were determined.2. In order to understand the polymerization mechanism MMA by of clusters Ln2(OCH₂CH₂NMe₂)12(OH)2Na8 as single-component catalyst, the reactions of clusters 1 and 5 respectively with MMA in 1:2 molar ratio were conducted. The intermediates Ln₂Na₆(OCH₂CH₂NMe₂)10[OOCC(CH₃)CH₂]₂ (Ln = Pr 8; Y 9) were isolated and fully characterized including X-ray crystal structural analyses. Complexes 8 and 9 have the same structure framework only the intermediate 8 contains one solvated DME molecule.3. The comparative study on the polymerization of MMA using clusters Ln2Na8(OCH₂CH₂NMe₂)12(OH)2 and intermediates Ln₂Na₆(OCH₂CH₂NMe₂)10[OOCC(CH₃)CH₂]₂ as the catalysts respectively was conducted. The catalytic activity of intermediates was lower than those of clusters and isotactic content of polymers was higher than those obtained by clusters. The reason for the difference in catalytic activity may be attributed to the presence of NaOCH₂CH₂NMe₂ and MeOH in the polymerization systems with clusters. 4. Polymerization kinetics of MMA catalyzed by Yb2(OCH₂CH₂NMe₂)12(OH)2Na8 was measured. The conversions increase with the increasing polymerization time and the first order kinetic plot of Ln[Mo]/[M] versus polymerizatrom time was obtained. The molecular weights increase with increasing conversions and molecular weight distributions maintain almost unchanged. The present polymerization of MMA initiated by clusters possesses"living"character.5. The catalytic activity of lanthanide/sodium heterobimetallic alkoxide clusters Ln2Na8(OCH₂CH₂NMe₂)12(OH)2 (Ln = Nd 2; Sm 3; Yb 4) for the polymerization of acrylonitrile was examined. They can act as active single-component catalyst for the polymerization of acrylonitrile under mild reaction conditions. The activity is higher than the lanthanide catalysts reported previously. The microstructures of the resulting polymers were determined by 13C NMR to be atactic.6. Clusters Ln2Na8(OCH₂CH₂NMe₂)12(OH)2 (Ln = Pr 1; Nd 2; Sm 3; Yb 4; Y 5) are found to be high active catalysts for amidation of aldehydes with amines. The present systems proceed smoothly with low loading of catalyst under mild reaction conditions. The systems have the advantage of tolerance to various substrates.7. Reaction of sodium aryloxide NaOAr (ArO = 2,6-di-tert-butyl-phenoxide) with LnCl3 in 4:1 molar ratio gave the corresponding anionic complexes [Ln(OAr)₄][Na(DME)₃] (Ln = Nd 10; Sm 11; Y 12)。8. Reaction of sodium aryloxide NaOAr (ArO = 2,6-di-tert-butyl-phenoxide) with LnCl3 in 3:1 molar ratio gave the four complexes Ln(OAr)3(THF)2 (Ln = Nd 15, Sm 16, Y 17, Yb 20)。9. Complexes [Ln(OAr)₄][Na(DME)₃] are found to be high active catalysts for amidation of aldehydes with amines. The present systems proceed smoothly with low catalyst loading under mild reaction conditions. Moreover, the systems have the advantage of tolerance to various substrates. Their activities are higher than those of the corresponding neutral ones10. The guanylation of amines with carbodiimide with complexes Ln(OAr)3(THF)2 as catalysts was studied. The results demonstrated that the complexes Ln(OAr)3(THF)2 are efficient catalysts for the guanylation reaction. The systems have the advantage of tolerance to various substrates.