Electronic Effects in Asymmetric Catalysis. Synthesis and Structure of Model Rhodium Complexes Containing Ferrocenyl Ligands for Use in the Hydroboration Reaction
Electronic Effects in Asymmetric Catalysis. Synthesis and Structure of Model Rhodium Complexes Containing Ferrocenyl Ligands for Use in the Hydroboration Reaction
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DOI：
10.1021/om9605995
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发表时间：
1997-01
期刊：
影响因子：
2.8
通讯作者：
A. Schnyder;Andrea Togni;U. Wiesli
中科院分区：
文献类型：
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作者：
A. Schnyder;Andrea Togni;U. Wiesli
通过相应的 P,N 配体 (1a−p) 与 [Rh(1,5-COD)2]BF4、[Rh(CO)2Cl]2 和 [Rh(COE)2Cl]2 的反应，以良好的收率获得了一系列具有手性二茂铁基螯合配体的新型铑络合物。通过测量化合物 5a−p 中的羰基伸缩振动来评估 P,N 配体的电子影响。已经发现了此类配合物的ν(CO)值与利用相应配体在Rh催化的苯乙烯硼氢化反应中获得的对映选择性之间的定性趋势相关性。因此，吡唑上的给电子基团和膦上的吸电子取代基都会导致更高的对映选择性和更高的CO伸缩频率。化合物[{1-{(S)-1-[(R)-2-(二苯基膦基)二茂铁基]乙基}-3,5-二甲基-1H-吡唑}Rh(1,5-COD)]BF4 (3a)， [{1-{(S)-1-[(R)-2-(二苯基膦)二茂铁基]乙基}-3,5-双(三氟甲基)-1H-吡唑}...
A series of new rhodium complexes with chiral ferrocenyl chelating ligands containing a tertiary phosphine and a pyrazole moiety have been obtained in good yields from the reaction of the corresponding P,N ligand (1a−p) with [Rh(1,5-COD)2]BF4, [Rh(CO)2Cl]2, and [Rh(COE)2Cl]2. The electronic influence of the P,N ligands has been evaluated by the measurement of the carbonyl stretching vibration in the compounds 5a−p. Qualitative trend correlations between ν(CO) values for such complexes and the enantioselectivities obtained in the Rh-catalyzed hydroboration of styrene utilizing the corresponding ligands have been found. Thus, both electron-donating groups on the pyrazole and electron-withdrawing substituents on the phosphine lead to both higher enantioselectivities and higher CO stretching frequencies. The compounds [{1-{(S)-1-[(R)-2-(diphenylphosphino)ferrocenyl]ethyl}-3,5-dimethyl-1H-pyrazole}Rh(1,5-COD)]BF4 (3a), [{1-{(S)-1-[(R)-2-(diphenylphosphino)ferrocenyl]ethyl}-3,5-bis(trifluoromethyl)-1H-pyrazole}...