Automated parallel screening using a series of in situ generated platinum(0) phosphine complexes has allowed the identification of improved catalysts for the diboration of alkynes using bis(pinacolato)diboron (B2(pin)2, pin = OCMe2CMe2O). A selection of phosphines were added to [Pt(NBE)3] (NBE = norbornene), which contains only labile mono-olefin ligands, and the activity of the resulting solutions as catalysts for the diboration of 4-CF3C6H4CCC6H4CF3-4′
1 by B2(pin)2 was investigated by in situ GC-MS and/or NMR spectroscopy. This allowed the optimum phosphine ∶ platinum stoichiometry to be identified as 1 ∶ 1, and the large differences in catalyst activity depending on the nature of the phosphine to be quantified. The best phosphines employed in the study, PCy3 and PPh2(o-Tol) (o-Tol = C6H4Me-o), give activities orders of magnitude greater than the worst, such as P(C6F5)3 and PBut3. The monophosphine catalysts function much more efficiently than previous catalysts for a range of alkynes allowing diborations to be performed at ambient temperatures. The diboration of strained cyclic alkenes and some vinyl- and allyl-arenes proceeded well, although the catalysts were inactive for other olefinic systems examined. As a result of these studies, the isolable and stable compound [Pt(PCy3)(η2-C2H4)2] was identified as an excellent catalyst for alkyne diboration even at room temperature.
p
使用一系列原位生成的
铂(0)
磷烯复合物进行的自动化平行筛选,使得能够识别出使用双(匹卡醇)二
硼(B2(pin)2, pin = OCMe2CMe2O)对
炔烃进行双
硼化的改进催化剂。选择了一些
磷烯添加到仅含有可交换的单烯
配体的[Pt(NBE)3](NBE = 脱氢诺尔本烯),并通过原位气相色谱-质谱(GC-MS)和/或核磁共振(NMR)光谱研究了所得溶液作为催化剂对4-CF3C6H4CCC6H4CF3-4'的双
硼化反应的活性。这使得最佳的
磷烯∶
铂化学计量比被识别为1∶1,并且能够量化根据
磷烯性质所产生的催化剂活性的大差异。在研究中使用的最佳
磷烯,PCy3和PPh2(o-Tol)(o-Tol = C6H4Me-o),其活性比最差的催化剂,如P(
C6F5)3和PBut3高几个数量级。单
磷烯催化剂在多种
炔烃中表现出比之前催化剂更高的效率,使得在常温下可以进行双
硼化反应。尽管催化剂在其他烯烃系统中无活性,但在应变环烯烃和一些
乙烯-和烯丙基-
芳烃的双
硼化中效果良好。这些研究的结果表明,分离和稳定的化合物[Pt(PCy3)(η2-
C2H4)2]被识别为即使在常温下也能作为优秀的
炔烃双
硼化催化剂。