Aluthge D C, Ahn J M, Mehrkhodavandi P
Department of Chemistry , University of British Columbia , 2036 Main Mall , Vancouver , BC V6T 1Z1 , Canada . Email:
Chem Sci. 2015 Sep 1;6(9):5284-5292. doi: 10.1039/c5sc01584g. Epub 2015 Jul 6.
A methodology for controlling aggregation in highly active and isoselective indium catalysts for the ring opening polymerization of racemic lactide is reported. A series of racemic and enantiopure dinuclear indium ethoxide complexes bearing salen ligands [(ONNO)InOEt] (R = Br, Me, admantyl, cumyl, -Bu) were synthesized and fully characterized. Mononuclear analogues (ONNO)InOCHPyr (R = Br, -Bu, SiPh) were synthesized by controlling aggregation with the use of chelating 2-pyridinemethoxide functionality. The nuclearity of metal complexes was confirmed using PGSE NMR spectroscopy. Detailed kinetic studies show a clear initiation period for these dinuclear catalysts, which is lacking in their mononuclear analogues. The polymerization behavior of analogous dinuclear and mononuclear compounds is identical and consistent with a mononuclear propagating species. The isotacticity of the resulting polymers was investigated using direct integration and peak deconvolution methodologies and the two were compared.
报道了一种用于控制用于外消旋丙交酯开环聚合的高活性和等规选择性铟催化剂中聚集现象的方法。合成并充分表征了一系列带有席夫碱配体[(ONNO)InOEt]（R = Br、Me、金刚烷基、枯基、-Bu）的外消旋和对映纯双核乙醇铟配合物。通过使用螯合的2-吡啶甲氧基官能团控制聚集来合成单核类似物(ONNO)InOCHPyr（R = Br、-Bu、SiPh）。使用PGSE NMR光谱确认了金属配合物的核数。详细的动力学研究表明这些双核催化剂有明显的引发期，而它们的单核类似物则没有。类似的双核和单核化合物的聚合行为相同，并且与单核增长物种一致。使用直接积分和峰去卷积方法研究了所得聚合物的等规度，并对两者进行了比较。
