Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada.
J Am Chem Soc. 2012 Apr 4;134(13):5893-9. doi: 10.1021/ja211658t. Epub 2012 Mar 26.
Investigation into the mechanism of transfer hydrogenation using trans-[Fe(NCMe)CO(PPh(2)C(6)H(4)CH═NCHR-)(2)]BF(4), where R = H (1) or R = Ph (2) (from R,R-dpen), has led to strong evidence that the active species in catalysis are iron(0) nanoparticles (Fe NPs) functionalized with achiral (with 1) and chiral (with 2) PNNP-type tetradentate ligands. Support for this proposition is given in terms of in operando techniques such as a kinetic investigation of the induction period during catalysis as well as poisoning experiments using substoichiometric amounts of various poisoning agents. Further support for the presence of Fe(0) NPs includes STEM microscopy imaging with EDX analysis, XPS analysis, and SQUID magnetometry analysis of catalytic solutions. Further evidence of Fe NPs acting as the active catalyst is given in terms of a polymer-supported substrate experiment whereby the NPs are too large to permeate the pores of a functionalized polymer. Final support is given in terms of a combined poisoning/STEM/EDX experiment whereby the poisoning agent is shown to be bound to the Fe NPs. This paper provides evidence of a rare example of asymmetric catalysis with nonprecious metal, zerovalent nanoparticles.
使用反式-[Fe(NCMe)CO(PPh(2)C(6)H(4)CH═NCHR-)(2)]BF(4)（其中 R = H (1) 或 R = Ph (2)（来自 R,R-dpen））进行转移氢化反应的机理研究，为催化反应中活性物种是铁(0)纳米颗粒（Fe NPs）的结论提供了有力的证据，这些 Fe NPs 用非手性（用 1）和手性（用 2）的 PNNP 型四齿配体进行了功能化。这种说法的依据是一些原位技术，例如在催化过程中诱导期的动力学研究，以及使用各种亚化学计量的毒化剂进行的毒化实验。存在 Fe(0) NPs 的进一步证据包括使用 STEM 显微镜成像和 EDX 分析、XPS 分析以及催化溶液的 SQUID 磁强计分析。进一步证明 Fe NPs 作为活性催化剂存在的证据是在聚合物负载的底物实验中，由于 NPs 太大而无法渗透功能化聚合物的孔。最后，通过结合毒化/STEM/EDX 实验提供了证据，表明毒化剂与 Fe NPs 结合。本文提供了一个非贵金属、零价纳米颗粒的不对称催化的罕见例子的证据。
