featuring a bridging hydride ligand between the iron and the boron atoms. Along the same line, 1,3-dienes bind well to 2 but undergo spontaneous activation if allylic C–H bonds are present; the resulting hydride is transferred to a residual ethylene ligand, as manifest in the formation of the cyclopentadienyl ethyl complex 22. The same elementary steps surface in a remarkable reaction cascade comprising
配合物[(dippp)Fe(C 2 H 4)2 ](2)和[CpFe(C 2 H 4)2 ] [Li·(tmeda)](5)都含有形式上为零价的铁中心,但表现出明显不同催化性能。尽管5能够诱导广泛的环异构化和环加成反应,2到目前为止,基本上仅限于炔烃和腈的环三聚。对两种复杂的相对于不饱和基材的行为的研究提供了对这种独特行为的可能起源的见解。因此,发现普通末端或内部烯烃不更换连接的乙烯单元2,而较强的π -受体配体1,5-环辛二烯,2-降冰片烯,和二苯基乙炔,得到相应的π络合物8,9,10,和13。参与氧化环化并形成相应金属环12的环丙烯衍生物。烯丙基-9-BBN或烯基-9-BBN衍生物屈服于烯丙基CH活化,并形成了非正统的烯丙基铁配合物25和27,其特征是铁和硼原子之间具有桥联氢化物配体。同样地,如果存在烯丙基CH键,则1,3-二烯与2结合良好,但会自发活化。如形成环戊二烯基乙基络合物22
Elementary Steps of Iron Catalysis: Exploring the Links between Iron Alkyl and Iron Olefin Complexes for their Relevance in CH Activation and CC Bond Formation
iron center. The resulting complex has a diene dihydride character in solution (15), whereas its structure in the solid state is more consistent with an η3‐allyl iron hydride rendition featuring an additional agosticinteraction (14). Finally, the preparation of the cyclopentadienyl iron complex 25 illustrates how an iron‐mediated C–H activation cascade can be coaxed to induce a stereoselective CC bond