The marked influence of steric and electronic properties of ancillary pyridylthioether ligands on the rate of allene insertion into the palladium–carbon bond
作者:Luciano Canovese、Fabiano Visentin、Gavino Chessa、Claudio Santo、Paolo Uguagliati、Giuliano Bandoli
DOI:10.1016/s0022-328x(02)01145-2
日期:2002.5
has been studied by 1H-NMR and UV–vis techniques. The rate of reaction appears to be strongly influenced by the steric and electronic properties of the ancillary ligand. The distortion induced by the substituent R′ in position 6 of the pyridine ring on the main coordination plane of the substrate (allowed by sulphur sp3 hybridisation) renders the substrate itself more prone to nucleophilic attack by the
合成了含有吡啶硫基醚辅助配体(R'NSR)(R'= H,Me,Cl; R = Me,Et,i -Pr,t -Bu,Ph)的中性甲基和酰基钯氯络合物,并合成通过元素分析和光谱学方法表征。1 H-NMR和UV-vis技术研究了这些络合物对插入钯-碳键中的丙二烯的反应性(丙二烯= DMA = 1,1-二甲基丙二烯; TMA = 1,1,3,3-四甲基丙二烯)。反应速率似乎受辅助配体的空间和电子性质强烈影响。由底物主配位平面上吡啶环6位上的取代基R'引起的形变(由硫sp 3允许)杂交)使底物本身更容易受到丙二烯的亲核攻击。通过降低NS部分中螯合原子的碱度,可进一步提高丙二烯插入的速率,这会导致钯核的亲电性增加,因此,在含有配体的配合物的情况下,测得的速率常数到目前为止,对于类似的反应,6-氯-2-苯基硫代甲基吡啶(ClN = SPh)是最大的。此外,在详尽研究所有相关吡啶基硫醚甲基配合物的行为