Single monodentate N-donor ligands versus multi-ligand analogues in Pd(II)-catalysed C–C coupling at reduced temperatures
作者:Abiodun Omokehinde Eseola、Helmar Görls、Joseph Anthony Orighomisan Woods、Winfried Plass
DOI:10.1016/j.poly.2020.114507
日期:2020.5
characterized and studied as N-stabilized precatalysts. Ligand donor strengths were spectroscopically estimated by protonation-deprotonation equilibria. The palladium(II) complexes were obtained in three coordination environments; (i) the mono-ligand complexes bearing trans-solvent co-ligands (PdL.acn and PdL.dmf), (ii) the chlorido-bridged dimers µ-(PdL)2 and (iii) the trans-bis-ligand PdL2 complexes
摘要降低工作温度的部署在工业上是有益的,并且高效,基于膦的预催化剂的使用受到其高成本和难以获得的制备程序的限制。为了研究配位环境对降低温度下催化剂反应活性的影响,认为设计带有单个单齿N-供体配体的钯(II)配合物是必要的。因此,2-(噻吩-2-基)-1H-咪唑配体(1-8),2,4,5-三苯恶唑(9)和2-(1H-咪唑-2-基)的二氯钯(II)配合物吡啶(10)已被制备,结构表征并作为N稳定的预催化剂进行了研究。通过质子化-去质子化平衡在光谱上估计配体的供体强度。在三个配位环境中获得了钯(II)配合物。(i)带有反溶剂共配体的单配体配合物(PdL.acn和PdL.dmf),(ii)氯桥联的二聚体µ-(PdL)2和(iii)反双配体PdL2复合体。考虑到环境温度操作,相对于先前报道的N-稳定的钯预催化剂,单齿单配体配位设计获得的催化结果代表了温度和反应时间的改进。单配体预催化剂可在40°C的