Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and Their Catalytic Activity for Hydrogenation and Conjugate Reduction
Synthesis of NHC-Oxazoline Pincer Complexes of Rh and Ru and Their Catalytic Activity for Hydrogenation and Conjugate Reduction
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DOI：
10.1021/acs.organomet.6b00239
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发表时间：
2016-06-13
期刊：
影响因子：
2.8
通讯作者：
Nishiyama, Hisao
中科院分区：
文献类型：
--
作者：
Ito, Jun-ichi;Sugino, Kanae;Nishiyama, Hisao
本文报道了含氮杂恶唑啉配体的新型CCN钳形Rh和Ru配合物的制备及其催化反应。恶唑啉基-苯基-咪唑鎓衍生物（3）是用于CCN钳形支架的合适的配体前体。用RhCl 3活化3的C-H键。3 H（2）O在NEt 3的存在下以13-27%的产率产生了所需的CCN钳形Rh配合物5。在NaOAc存在下，通过对伞花烃Ru配合物7的C-H键活化，以良好的产率合成了相关的CCN钳形Ru配合物8-10。配合物8和配合物9根据CO和OAc配体的配位关系，具有两种非对映异构体。CCN Rh配合物对β-甲基肉桂酸乙酯与氢硅烷的共轭还原反应具有催化活性，且具有中等的对映选择性。CCN Ru配合物在芳香酮的加氢反应中表现出良好的催化活性。特别地，9-乙酰基蒽的氢化不仅发生在C=O键上，而且还发生在蒽环上。钌配合物也被用作催化剂在9-乙酰基蒽与2-丙醇的转移氢化;再次，C=O键和蒽环被氢化。
We describe the preparation and catalytic reactions of new CCN pincer Rh and Ru complexes containing NCH-oxazoline hybrid ligands. Oxazolinyl-phenyl-imidazolium derivatives (3) were suitable ligand precursors for the CCN pincer scaffold. C-H bond activation of 3 with RhCl3. 3H(2)O in the presence of NEt3 yielded the desired CCN pincer Rh complexes 5 in 13-27% yields. The related CCN pincer Ru complexes 8-10 were synthesized in good yields by C-H bond activation of p-cymene Ru complexes 7 in the presence of NaOAc in DMF. The chiral complexes 8 and 9 had two diastereomers according to the coordination of CO and OAc ligands. The CCN Rh complexes showed catalytic activity for conjugate reduction of ethyl beta-methylcinnamate with hydrosilane, with moderate enantioselectivity. The CCN Ru complexes were found to be active in the hydrogenation of aromatic ketones. In particular, hydrogenation of 9-acetylanthracene took place at not only the C=O bond but also the anthracene ring. The Ru complexes were also used as catalysts in the transfer hydrogenation of 9-acetylanthracene with 2-propanol; again, both the C=O bond and the anthracene ring were hydrogenated.