Triazolylidene Iridium Complexes for Highly Efficient and Versatile Transfer Hydrogenation of C═O, C═N, and C═C Bonds and for Acceptorless Alcohol Oxidation
作者:Zahra Mazloomi、René Pretorius、Oscar Pàmies、Martin Albrecht、Montserrat Diéguez
DOI:10.1021/acs.inorgchem.7b01707
日期:2017.9.18
oxidation. High-valent iridium(III) complexes were identified as the most active precursors for the oxidative alcohol dehydrogenation, while a low-valent iridium(I) complex with a methyl ether functionality was most active in reductive transfer hydrogenation. This catalyst precursor is highly versatile and efficiently hydrogenates ketones, aldehydes, imines, allylic alcohols, and most notably also unpolarized
据报道,一组铱(I)和铱(III)配合物带有三唑基亚烷基配体,这些配体包含苯并恶唑,噻唑和甲基醚侧基作为潜在的螯合供体位点。这些基团的键合模式通过NMR光谱和X射线结构分析来鉴定。在转移氢化和无受体醇氧化中,将该配合物评价为催化剂前体。高价铱(III)配合物被确定为氧化醇脱氢最活跃的前体,而具有甲基醚官能团的低价铱(I)配合物在还原转移氢化中最活跃。这种催化剂的前体用途广泛,可以有效地氢化酮,醛,亚胺,烯丙基醇,尤其是非极化烯烃,转移加氢反应非常困难的基质。周转频率高达260小时记录了–1的烯烃氢化反应,而氢转移到酮和醛中的最大周转频率大于2000 h –1。结合同位素标记实验,动力学同位素效应测量和Hammett参数相关性进行的机械研究表明,限制转移的步骤是转移氢化过程中金属从氢化物向基质的氢化物转移,而在醇脱氢中,限制步骤是基质协调到金属中心。