Reversible C-C Bond Formation between Redox-Active Pyridine Ligands in Iron Complexes
Reversible C-C Bond Formation between Redox-Active Pyridine Ligands in Iron Complexes
复制标题
DOI：
10.1021/ja305679m
复制
发表时间：
2012-12-19
影响因子：
15
通讯作者：
Holland, Patrick L.
中科院分区：
文献类型：
--
作者：
Dugan, Thomas R.;Bill, Eckhard;Holland, Patrick L.
本文描述了形式铁(I)络合物(LFe)-Fe-Me(Py-R)(2)(L-Me=大体积β-二酮酸根；R=H，4-TBU)，其中吡啶基配体优先接受显著的未配对自旋密度。对4-叔丁基吡啶配合物的结构、光谱和计算研究表明，S=3/2物种是(A)与吡啶阴离子发生反铁磁性偶联的高自旋铁(II)和(B)高自旋铁(I)的共振杂化。当吡啶缺乏叔丁基团的保护时，它会迅速且可逆地发生自由基偶联反应，形成新的C-C键。在一个反应中，配位的吡啶偶联到三苯甲基自由基，在另一个反应中，它二聚生成吡啶衍生的二阴离子，连接两个铁(II)离子。二聚体中快速、可逆的C-C键的形成将来自正式还原的金属的电子存储为配体中的C-C键，通过使用偶合的双铁(II)络合物生成已知来自铁(I)前体的产物来证明。
This manuscript describes the formally iron(I) complexes (LFe)-Fe-Me(Py-R)(2) (L-Me = bulky beta-diketiminate; R = H, 4-tBu), in which the basal pyridine ligands preferentially accept significant unpaired spin density. Structural, spectroscopic, and computational studies on the complex with 4-tert-butylpyridine ((tBu)py) indicate that the S = 3/2 species is a resonance hybrid between descriptions as (a) high-spin iron(II) with antiferromagnetic coupling to a pyridine anion radical and (b) high-spin iron(I). When the pyridine lacks the protection of the tert-butyl group, it rapidly and reversibly undergoes radical coupling reactions that form new C-C bonds. In one reaction, the coordinated pyridine couples to triphenylmethyl radical, and in another, it dimerizes to give a pyridine-derived dianion that bridges two iron(II) ions. The rapid, reversible C-C bond formation in the dimer stores electrons from the formally reduced metal as a C-C bond in the ligands, as demonstrated by using the coupled diiron(II) complex to generate products that are known to come from iron(I) precursors.