Ring-opening polymerization of l-lactide by organotin(IV)alkoxides, R2Sn(OPri)2: Estimation of the activation parameters
摘要:
The ring-opening polymerization of L-lactide, L-LA, to give poly-L-lactide by R2Sn(OPri)(2) compounds, where R = Bu-n and p-XC6H4 (X = CF3, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in Delta H not equal as a function of R with all the values falling within the range 11 +/- 2 kcal mol(-1). The entropy of activation, Delta S not equal, is consistently large and negative, -50 +/- 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph2Sn(OPri)(2), (p-FC6H4)(2)Sn(OPri)(2) and (p-Me2NC6H4)(3)SnOPri are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPri ligands. (c) 2007 Published by Elsevier Ltd.
Biddle, Brian N.; Gray, John S.; Crowe, Alan J., Journal of the Chemical Society, Dalton Transactions
作者:Biddle, Brian N.、Gray, John S.、Crowe, Alan J.
DOI:——
日期:——
“Push–push and push–pull” polystannanes
作者:J. S. Dhindsa、B. F. Jacobs、A. J. Lough、D. A. Foucher
DOI:10.1039/c8dt03043j
日期:——
moieties attached to the tin backbone are described. Precursor tetra aryl- (1, 2) stannanes were converted to mono- (3) and dichloro- (4, 5) stannanes by either sequential chlorination or by redistribution reactions with SnCl4. Compounds 4 and 5 were transformed to polymerisable tin dihydride monomers 6 and 7 using a large excess (10×) of NaBH4. Homopolymer 8 with electron donating aryl substituents (p-MeOC6H4-)
描述了锡锡骨架上带有“推”或“拉”部分的聚锡烷的合成和表征。前体的四芳基- (1,2)锡烷转化成单- (3)和二氯- (4,5)由任一顺序氯化或通过用的SnCl再分配反应锡烷4。使用大量过量的(10x)NaBH 4将化合物4和5转化为可聚合的二氢化锡单体6和7。具有给电子芳基取代基的均聚物8(p -MeOC 6使用威尔金森氏催化剂通过脱氢聚合合成H 4-)。尝试使用相似的条件由7的脱氢偶联制备具有吸电子芳基取代基(p -CF 3 C 6 H 4-)的均聚物9,仅导致形成低分子量的低聚物。通过(n -Bu)2 Sn(NEt 2)2与单体6或7的缩聚反应合成了两种交替的聚合物10和11。。第一种是“推-推”交替聚合物10,它由一个重复单元组成,该重复单元在相邻的锡中心处由两个不同的供电子基团(p -MeOC 6 H 4-,n -Bu )组成。第二种是“推挽式”交替聚合物11,在相邻的锡原子上同时带有给电子基团(n
Ring-opening polymerization of l-lactide by organotin(IV)alkoxides, R2Sn(OPri)2: Estimation of the activation parameters
作者:Malcolm H. Chisholm、Judith C. Gallucci、Clemens Krempner
DOI:10.1016/j.poly.2007.06.002
日期:2007.9
The ring-opening polymerization of L-lactide, L-LA, to give poly-L-lactide by R2Sn(OPri)(2) compounds, where R = Bu-n and p-XC6H4 (X = CF3, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in Delta H not equal as a function of R with all the values falling within the range 11 +/- 2 kcal mol(-1). The entropy of activation, Delta S not equal, is consistently large and negative, -50 +/- 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph2Sn(OPri)(2), (p-FC6H4)(2)Sn(OPri)(2) and (p-Me2NC6H4)(3)SnOPri are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPri ligands. (c) 2007 Published by Elsevier Ltd.