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A variety of allylic, aza-allylic and 1,5-diazapentadienyllanthanide compounds were synthesized and their polymerization catalysis toward methyl methacrylate were examined. Divalent Sm[1,3-bis(trimethylsilyl)propenyl]2(THF)2 1 and Sm(1,3-diphenylpropenyl)2(THF)2 2 were synthesized by the reaction of potassium 1,3-bis(trimethylsilyl)propenide or potassium 1,3-diphenylpropenide with SmI2. The aza-allyllanthanide compound was synthesized by the reaction of 2-pyridylbenzyllithium with SmCl3 followed by the reaction with LiCH(SiMe3)2 to give (2-pyridylbenzyl)2SmCH(SiMe3)2 3. 1,5-Diazapentadienyllanthanide was prepared by the reaction of K[(C5H4N)2CPh] with YbBr2 to give Yb[(C5H4N)2CPh]2(THF)2 4, which crystalizes monoclinic, space group C2/C (No. 15), with a=35.19(1), b=13.613(3), c=26.552(7) A, β=133.77(1)°, and Z=8. Preparations of divalent samarium and ytterbium complexes with bis(2-pyridylphenylmethyl)dimethylsilane ligand (6 and 7) were carried out by the reaction of dipotassium salt of bis(2-pyridylphenylmethyl)dimethylsilane with SmI2 or YbBr2. By using the resulting compounds 1, 2, 3, 4, 6 and 7 as initiator, we have examined their catalytic activities for the polymerization of methyl methacrylate and found that compounds 6 and 7 are effective to give high molecular weight isotactic polymers. |
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