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Synthesis, Characterization, and Catalytic Properties of Iridium Pincer Complexes Containing NH Linkers
Organometallics ( IF 2.5 ) Pub Date : 2017-12-19 00:00:00 , DOI: 10.1021/acs.organomet.7b00713 Reuben B. Leveson-Gower 1 , Paul B. Webb 1 , David B. Cordes 2 , Alexandra M. Z. Slawin 2 , David M. Smith 1 , Robert P. Tooze 1 , Jianke Liu 1
Organometallics ( IF 2.5 ) Pub Date : 2017-12-19 00:00:00 , DOI: 10.1021/acs.organomet.7b00713 Reuben B. Leveson-Gower 1 , Paul B. Webb 1 , David B. Cordes 2 , Alexandra M. Z. Slawin 2 , David M. Smith 1 , Robert P. Tooze 1 , Jianke Liu 1
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A series of tert-butyl-substituted pincer ligands based on 1,3-diaminobenzene and 3-aminophenol scaffolds, tBu4PXCYP (1e, X = Y = NH; 1f, X = NH; Y = O) and the corresponding iridium hydridochloro complexes (tBu4PXCYP)IrHCl (2e, X = Y = NH; 2f, X = NH; Y = O) were prepared with moderate yields and high purity and were fully characterized by 1H and 31P NMR spectroscopy. Unsymmetrical hybrid pincer ligands R2PNCOPtBu2 (1g, R = isopropyl; 1h, R = cyclohexyl) were prepared conveniently in high yield via a one-pot procedure by judiciously choosing reaction conditions and base; the corresponding iridium hydrido chloro complexes iPr2PNCOPtBu2IrHCl (2g) and Cy2PNCOPtBu2IrHCl (2h) were synthesized by the reaction of [IrCl(COE)2]2 with ligands. X-ray crystallography reveals that these iridium pincer complexes adopt similar square-pyramidal geometries and exhibit strong intermolecular hydrogen bonding between the NH linker and chloride ions of the adjacent iridium complex in the solid state. 1H NMR chemical shifts of tert-butyl based pincer ligated iridium hydrides move downfield when the electronegativity of the linker between the benzene backbone and phosphine moiety increases for 2a, 2e, 2f, and 2b. Accordingly the corresponding iridium pincer carbonyl complexes (tBu4PXCYP)Ir(CO), 3a, 3e, 3f, and 3b show a blue shift in the CO stretching frequency. The activities of iridium complexes containing NH linkers were briefly examined for transfer dehydrogenation from cyclooctane to tert-butylethylene; (iPr2PNCOPtBu2)IrHCl (2g) exhibits the highest activity among all tested iridium pincer complexes, including the most studied (tBu4PCP)IrHCl (2a) and (tBu4POCOP)IrHCl (2b). The enhanced catalytic activity could be related to combined electronic and steric effects of the NH/O hybrid linker and different alkyl groups at phosphorus. This new class of iridium pincer complexes could have great implications in catalytic transformation of polar compounds due to the strong hydrogen-bond-donating ability of the NH linker.
中文翻译：
含NH键的铱钳配合物的合成，表征及催化性能
基于1,3-二氨基苯和3-氨基酚骨架的一系列叔丁基取代的钳位配体，tBu4 PXCYP（1e，X = Y = NH; 1f，X = NH; Y = O）和相应的铱氢化氯络合物（tBu4 PXCYP）IrHCl（2e，X = Y = NH; 2f，X = NH; Y = O）的制备具有中等收率和高纯度，并通过1 H和31 P NMR光谱进行了全面表征。不对称杂种钳配体R2 PNCOP tBu2（1g，R =异丙基; 1h通过明智地选择反应条件和碱，通过一锅法方便地以高收率制备R，（R ＝环己基）。通过[IrCl（COE）2 ] 2与配体的反应合成了相应的铱氢化氯络合物iPr2 PNCOP tBu2 IrHCl（2g）和Cy2 PNCOP tBu2 IrHCl（2h）。X射线晶体学表明，这些铱钳形配合物采用相似的正方形-金字塔形几何形状，并且在固态下，相邻的铱配合物的NH连接子和氯离子之间显示出很强的分子间氢键。叔丁基的1 H NMR化学位移当苯骨架和膦部分之间的连接基的电负性增加2a，2e，2f和2b时，基于丁基的钳式氢化铱氢化物向低位移动。因此，相应的铱夹钳羰基配合物（tBu4PXCYP）Ir（CO），3a，3e，3f和3b在CO拉伸频率中显示出蓝移。简要检查了含NH连接基的铱配合物的活性，以研究其从环辛烷到叔丁基乙烯的转移脱氢；（iPr2 PNCOP tBu2）IrHCl（2克）在所有经过测试的铱夹钳复合物中表现出最高的活性，包括研究最多的（tBu4 PCP）IrHCl（2a）和（tBu4 POCOP）IrHCl（2b）。增强的催化活性可能与NH / O杂化接头和磷中不同烷基的组合电子和空间效应有关。由于NH接头具有很强的氢键给体能力，因此这类新型的铱钳形配合物可能会对极性化合物的催化转化产生重大影响。
更新日期：2017-12-19
中文翻译：
含NH键的铱钳配合物的合成，表征及催化性能
基于1,3-二氨基苯和3-氨基酚骨架的一系列叔丁基取代的钳位配体，tBu4 PXCYP（1e，X = Y = NH; 1f，X = NH; Y = O）和相应的铱氢化氯络合物（tBu4 PXCYP）IrHCl（2e，X = Y = NH; 2f，X = NH; Y = O）的制备具有中等收率和高纯度，并通过1 H和31 P NMR光谱进行了全面表征。不对称杂种钳配体R2 PNCOP tBu2（1g，R =异丙基; 1h通过明智地选择反应条件和碱，通过一锅法方便地以高收率制备R，（R ＝环己基）。通过[IrCl（COE）2 ] 2与配体的反应合成了相应的铱氢化氯络合物iPr2 PNCOP tBu2 IrHCl（2g）和Cy2 PNCOP tBu2 IrHCl（2h）。X射线晶体学表明，这些铱钳形配合物采用相似的正方形-金字塔形几何形状，并且在固态下，相邻的铱配合物的NH连接子和氯离子之间显示出很强的分子间氢键。叔丁基的1 H NMR化学位移当苯骨架和膦部分之间的连接基的电负性增加2a，2e，2f和2b时，基于丁基的钳式氢化铱氢化物向低位移动。因此，相应的铱夹钳羰基配合物（tBu4PXCYP）Ir（CO），3a，3e，3f和3b在CO拉伸频率中显示出蓝移。简要检查了含NH连接基的铱配合物的活性，以研究其从环辛烷到叔丁基乙烯的转移脱氢；（iPr2 PNCOP tBu2）IrHCl（2克）在所有经过测试的铱夹钳复合物中表现出最高的活性，包括研究最多的（tBu4 PCP）IrHCl（2a）和（tBu4 POCOP）IrHCl（2b）。增强的催化活性可能与NH / O杂化接头和磷中不同烷基的组合电子和空间效应有关。由于NH接头具有很强的氢键给体能力，因此这类新型的铱钳形配合物可能会对极性化合物的催化转化产生重大影响。
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