Solvent responsive catalyst improves NMR sensitivity via efficient magnetisation transfer.
Solvent responsive catalyst improves NMR sensitivity via efficient magnetisation transfer.
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DOI：
10.1039/c6cc03185d
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发表时间：
2016-06-28
期刊：
影响因子：
--
通讯作者：
Duckett SB
中科院分区：
文献类型：
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作者：
Ruddlesden AJ;Duckett SB
合成了一种双齿铱卡宾配合物Ir（κC，O-L1）（COD），它含有一个强给电子的卡宾配体，配体被一个顺式跨酚基团官能化。活化后，它通过改变其形式在一系列溶剂中充当有效的磁化转移催化剂。合成了一种双齿铱卡宾配合物Ir（κC，O-L1）（COD），它含有一个强给电子的卡宾配体，配体被一个顺式跨酚基团官能化。该络合物充当有效磁化转移催化剂的前体，所述催化剂在与H2和合适的双电子供体反应后形成。在含有吡啶的溶剂如苯中，它们的例子是具有不等价氢化物配体和Ir-O键保留的中性手性Ir（H）2（κC，O-L1）（py）2，而在甲醇中，Ir-O键断裂导致具有化学等价氢化物配体的两性离子[Ir（H）2（κC，O-L1）（py）3]+。因此，活性催化剂的形式取决于溶剂。这两种配合物打破了氢化物配体的磁对称性，并且在从仲氢到松散结合的配体的极化的催化转移中是活跃的。对吡啶、烟醛和尼古丁的测试结果显示，其1H NMR信号中的单自旋质子极化水平高达1.2%，而在9.4特斯拉下的正常水平为0.003%。这些结果说明了如何合理的催化剂设计产生具有良好SABRE活性的溶剂依赖性催化剂。
A bidentate iridium carbene complex, Ir(κC,O-L1)(COD), has been synthesised which contains a strongly electron donating carbene ligand that is functionalised by a cis-spanning phenolate group. Upon activation, it acts as an efficient magnetisation transfer catalyst in a range of solvents by varying its form. A bidentate iridium carbene complex, Ir(κC,O-L1)(COD), has been synthesised which contains a strongly electron donating carbene ligand that is functionalised by a cis-spanning phenolate group. This complex acts as a precursor to effective magnetisation transfer catalysts which form after reaction with H2 and a suitable two electron donor. In solvents such as benzene, containing pyridine, they are exemplified by neutral, chiral Ir(H)2(κC,O-L1)(py)2 with inequivalent hydride ligands and Ir–O bond retention, whilst in methanol, Ir–O bond cleavage leads to zwitterionic [Ir(H)2(κC,O–-L1)(py)3]+, with chemically equivalent hydride ligands. The active catalyst's form is therefore solvent dependent. Both these complexes break the magnetic symmetry of the hydride ligands and are active in the catalytic transfer of polarisation from parahydrogen to a loosely bound ligand. Test results on pyridine, nicotinaldehyde and nicotine reveal up to ≈1.2% single spin proton polarisation levels in their 1H NMR signals which compare to the normal 0.003% level at 9.4 Tesla. These results exemplify how rational catalyst design yields a solvent dependent catalyst with good SABRE activity.