Structural Modification of Functionalized Phosphine Sulfonate-Based Palladium(II) Olefin Polymerization Catalysts

The influence of phosphine sulfonate ligands bearing
a variety
of functionalities on the conformation of their derived Pd­(II) complexes
and their catalytic behavior in olefin polymerization reactions was
investigated. Analogous to the anisyl-derived 1a the
methyl thioether-substituted 8 as well as methoxylated
naphthalene-based compound 9 were successfully prepared.
NOESY NMR spectroscopy has been applied for the interpretation of
the complex configurations in solution and the correlation to the
corresponding molecular structures of 1a and 9. Ethene homopolymerization reactions were used for the determination
of reactivity trends and interpretation of effects originating from
the altered ligand substitution. Detailed analysis of the PE microstructure
shows that catalyst 9 acts as an efficient isomerization-type
catalyst during the formation of low molecular weight PE. Additionally
for compound 8 Pd–sulfur interactions with the
introduced methyl thioether functionalities are proposed, based on
NMR spectroscopic experiments. This catalyst promotes formation of
minimal amounts of high molecular weight PE. Comparison of 1a, 1b, 8, and 9 indicates that
the PE molecular weight is controlled by the protection of at least
one axial position of the palladium center, but no clear trends concerning
the catalyst activity could be observed.

本研究探究了带有多种官能团的膦磺酸盐配体，对其衍生的钯(II)（Pd(II)）配合物构象，以及其在烯烃聚合反应中的催化行为的影响。与茴香基衍生的钯(II)配合物1a类似，本研究成功合成了甲基硫醚取代的配体对应的配合物8，以及甲氧基化萘基衍生的化合物9。本研究采用核Overhauser效应核磁共振波谱（NOESY NMR）技术，解析了溶液中配合物的构型，并关联了1a与9的对应分子结构。通过乙烯均聚反应，本研究测定了反应活性趋势，并解析了配体取代基改变所带来的影响。对聚乙烯（PE）微观结构的详细分析表明，催化剂9在低分子量聚乙烯的生成过程中，可作为高效的异构化型催化剂发挥作用。此外，基于核磁共振波谱实验结果，本研究提出配合物8存在与引入的甲基硫醚官能团之间的钯-硫相互作用。该催化剂仅能促进极少量高分子量聚乙烯的生成。对1a、1b、8与9的对比分析表明，聚乙烯的分子量受钯中心至少一个轴向位点的保护作用调控，但未观察到催化剂活性存在明确的变化趋势。