Rare-Earth Metal Complexes Supported by 1,ω-Dithiaalkanediyl-Bridged Bis(phenolato) Ligands: Synthesis, Structure, and Heteroselective Ring-Opening Polymerization of rac-Lactide

作者: Haiyan Ma , Thomas P. Spaniol , Jun Okuda

DOI: 10.1021/IC702312B

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摘要: Monomeric yttrium and lutetium bis(phenolato) complexes [Ln(OSSO){N(SiHMe 2) 2}(THF)] (Ln = Y, Lu) were prepared from the reaction of silylamido [Ln{N(SiHMe 2} 3(THF) 2] with 1 equiv tetradentate 1,omega-dithiaalkanediyl-bridged bis(phenol) (OSSO)H 2 1- 9 in moderate to high yields. In contrast rigid configuration scandium analogues, 2b 3b complex 3c that contain a C bridge between two sulfur donors ligand are symmetric solution. The monomeric nature these was indicated by an X-ray diffraction study 6b. center 6b is coordinated [OSSO]-type ligand, one group THF oxygen located trans. Corresponding larger rare-earth metals could not be obtained similar reactions: Reaction [La{N(SiHMe 1,2-xylylene-linked gave dinuclear lanthanum 6d formula [La 2(OSSO) 3] inequivalent eight-coordinate metal centers. efficiently initiated ring-opening polymerization (ROP) lactides THF. heteroselectivity during ROP rac-lactide enhanced when steric demand increased, either extending length or introducing bulky ortho-substituents phenoxy units. A 3 within backbone essential allow configurational interconversion active site Lambda Delta polymerization, allowing accommodation both enantiomers monomer alternating fashion.

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