Study On The Activation Of Organic Molecules By Ytterbium (Ⅱ) Complex Bearing A Diamino Bis(Phenolate) Ligand

In this thesis, a study of [Me₂NCH₂CH₂N(CH₂-2-O-3,5-C₆H₂(^tBu)₂)₂]Yb(THF)₂ 1potential application as an one-electron-transfer reagent for the activation of organicmolecules, together with its catalytic activity for the ring-opening polymerization ofε-caprolactone were studied. The main results obtained are as follows:1. The reaction of complex 1 with PhNCO in a molar ratio of 1:1 was examined inTHF at room temperature, gave a reduction-coupling product[(YbLOCNPh)(THF)]₂·4THF 2, which is the fist reduction-coupling product ofPhNCO mediated by Yb (â…¡) complex. X-ray structural determination shows that incomplex 2 the dianionic oxamide ligand resulted from the reductive coupling of twophenyl isocyanate molecules coordinates to Yb atoms inμ,η⁴ fashion.2. Complex 1 reacts with PhC≡CH in a 1:1 molar ratio in THF at room temperature, togive an alkynide complex[Me₂NCH₂CH₂N(CH₂-2-O-3,5-C₆H₂(^tBu)₂)₂]YbC≡CPh(DME) 3, which is the firstmonomeric phenylacetynide ytterbium (â…¢) complex with a terminalphenylacetynide anion. In complex 3, the coordination of DME molecule completesthe seven-coordinated geometry around the Yb atom.3. The reaction of complex 1 with ⁱPr-N=C=N-ⁱPr in a molar ratio of 1:1 wasexamined in THF at room temperature. The reaction afforded the fist bridgedcarbene lanthanide complex{[Me₂NCH₂CH₂N(CH₂-2-O-3,5-C₆H₂(^tBu)₂)₂]Yb}₂(ⁱPr-NCN-ⁱpr) 4, which wasformed. Complex 4 was fully characterized by ¹³C NMR and X-ray diffraction.4. The reaction of complex 1 with Cy-N=C=N-Cy in a molar ratio of 1:1 wasexamined in THF at room temperature. The elemental analysis and ¹³C NMR of theorange red power suggested that it to be analogous complex {[Me₂NCH₂CH₂N(CH₂-2-O-3,5-C₆H₂(^tBu)₂)₂]Yb]₂(Cy-NCN-Cy) 5, although wehave not got any crystal suitable for X-ray determination.5. The catalytic activity of complex 1 was tested for the ring-opening polymerizationofε-caprolactone (CL). The activity of 1 is much higher than those found for Yb(â…¡)complexes recently published, however the system gives the polymers with ratherbroader molecular weight distributions resulted from transesterification reacton.6. Complex 1 showed high catalytic activity for the addition of PhC≡CH tocarbodiimides.7. Complex 4 does not react with NiCl₂·DME, Ph₃PO or Ph₃P indicating that complex4 is a stable enough.8. The reaction of complex 4 with PhNCO afforded a new complex{[Me₂NCH₂CH₂N(CH₂-2-O-3,5-C₆H₂(^tBu)₂)₂]Yb}₂(PhNCO)₂(PhN) 7. Theformation of 7 indicated the cleavage of CO from PhNCO was taken place along thereaction of carbene and PhNCO. The detailed mechanism for the formation of 7 hasnot been clearly yet.9. Complex 4 reacts with PhNCO in the present of NiCl₂·DME, gave a new complex[Me₂NCH₂CH₂N(CH₂-2-O-3,5-C₆H₂(^tBu)₂)₂]Yb(PhNCO)(PhN) 8. The mechanismfor the formation of 7 and 8 has not been clearly.