Synthesis and Hydrogenation Activity of Iron Dialkyl Complexes with Chiral Bidentate Phosphines

详细信息    查看全文

• 作者：Jordan M. Hoyt ; Michael Shevlin ; Grant W. Margulieux ; Shane W. Krska ; Matthew T. Tudge ; Paul J. Chirik
• 刊名：Organometallics
• 出版年：2014
• 出版时间：October 27, 2014
• 年：2014
• 卷：33
• 期：20
• 页码：5781-5790
• 全文大小：489K
• ISSN：1520-6041

文摘

The activity of bis(phosphine) iron dialkyl complexes for the asymmetric hydrogenation of alkenes has been evaluated. High-throughput experimentation was used to identify suitable iron鈥損hosphine combinations using the displacement of pyridine from py₂Fe(CH₂SiMe₃)₂ for precatalyst formation. Preparative-scale synthesis of a family of bis(phosphine) iron dialkyl complexes was also achieved using both ligand substitution and salt metathesis methods. Each of the isolated organometallic iron complexes was established as a tetrahedral and hence high-spin ferrous compound, as determined by M枚ssbauer spectroscopy, magnetic measurements, and, in many cases, X-ray diffraction. One example containing a Josiphos-type ligand, (SL-J212-1)Fe(CH₂SiMe₃)₂, proved more active than other isolated iron dialkyl precatalysts. Filtration experiments and the lack of observed enantioselectivity support dissociation of the phosphine ligand upon activation with dihydrogen and formation of catalytically active heterogeneous iron. The larger six-membered chelate is believed to reduce the coordination affinity of the phosphine for the iron center, enabling metal particle formation.