Improved Metathesis Lifetime: Chelating Pyridinyl-Alcoholato Ligands in the Second Generation Grubbs Precatalyst
作者:Jean du Toit、Margaritha Jordaan、Carlijn Huijsmans、Johannes Jordaan、Cornelia van Sittert、Hermanus Vosloo
DOI:10.3390/molecules19055522
日期:——
Hemilabile ligands can release a free coordination site “on demand” of an incoming nucleophilic substrate while occupying it otherwise. This is believed to increase the thermal stability and activity of catalytic systems and therefore prevent decomposition via free coordination sites. In this investigation chelating pyridinyl-alcoholato ligands were identified as possible hemilabile ligands for incorporation into the second generation Grubbs precatalyst. The O,N-alcoholato ligands with different steric bulk could be successfully incorporated into the precatalysts. The incorporation of the sterically hindered, hemilabile O,N-ligands improved the thermal stability, activity, selectivity and lifetime of these complexes towards the metathesis of 1-octene. A decrease in the activity of the second generation Grubbs precatalyst was additionally observed after incorporating a hemilabile O,N-ligand with two phenyl groups into the system, while increasing their lifetime.
半亲和配体可以 "按需 "释放进入的亲核底物的自由配位位点,而不占用该位点。这被认为可以提高催化系统的热稳定性和活性,从而防止通过游离配位位点发生分解。在这项研究中,螯合吡啶醇配体被确定为可能加入第二代格拉布斯前催化剂的可亲血配体。具有不同立体体积的 O,N-醇配体可以成功地加入到前催化剂中。掺入立体受阻的半亲和 O,N-配体提高了这些配合物在 1-辛烯偏析过程中的热稳定性、活性、选择性和寿命。此外,在体系中加入带有两个苯基的半亲和 O,N-配体后,第二代格拉布斯前催化剂的活性降低了,但寿命却延长了。