Electronic structure of bis(imino)pyridine iron dichloride, monochloride, and neutral ligand complexes: A combined structural, spectroscopic, and computational study
Electronic structure of bis(imino)pyridine iron dichloride, monochloride, and neutral ligand complexes: A combined structural, spectroscopic, and computational study
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DOI：
10.1021/ja064557b
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发表时间：
2006-10-25
影响因子：
15
通讯作者：
Chirik, Paul J.
中科院分区：
文献类型：
--
作者：
Bart, Suzanne C.;Chlopek, Krzysztof;Chirik, Paul J.
通过光谱和计算方法研究了双（亚氨基）吡啶铁二卤化物、单卤化物和中性配体化合物家族的电子结构。 ((i)PrPDl)FeCl2 ((i)PrPDl) 2,6- (2,6-(Pr2C6H3N)-Pr-i=CMe)(2)C5H3N) 的测量参数与穆斯堡尔光谱和磁数据相结合，建立了由中性双(亚氨基)吡啶配体连接的高自旋亚铁中心。将这些数据与单电子还原产物 ((i)PrPDl)FeCl 的数据进行比较，再次证明了高自旋亚铁离子，但在这种情况下，S-Fe = 2 金属中心与配体中心自由基 (S-L 1/2) 反铁磁耦合，解释了实验观察到的 S = 3/2 基态。继续还原为 ((PrPDI)-Pr-i)FeLn (L = N-2, n = 1,2; CO, n = 2; 4-(N,N-二甲氨基)吡啶, n = 1) 产生双重还原的双(亚氨基)吡啶双自由基，保留亚铁离子。 N,N-(二甲氨基)吡啶化合物的计算和实验数据均表明双(亚氨基)吡啶二价阴离子具有近等能的单线态 (S-L = 0) 和三线态 (S-L = 1) 形式。在两种自旋状态下，铁都是中间自旋 (S-Fe = 1) 亚铁。实验上，由于铁和配体三重态的反铁磁耦合，该化合物具有自旋单重态基态 (S = 0)。单线态双自由基激发态与配体的三线态基态通过自旋轨道耦合混合，产生与温度无关的顺磁性，并解释了在螯合物上观察到的面内质子的 H-1 NMR 化学位移的大分散性。总体而言，这些研究表明，用碱金属或硼氢化物试剂还原 ((i)PrPD1)FeCl2 会导致电子连续转移到配体的共轭 pi 系统而不是金属中心。
The electronic structure of a family of bis(imino) pyridine iron dihalide, monohalide, and neutral ligand compounds has been investigated by spectroscopic and computational methods. The metrical parameters combined with Mossbauer spectroscopic and magnetic data for ((i)PrPDl)FeCl2 ((i)PrPDl) 2,6- (2,6-(Pr2C6H3N)-Pr-i=CMe)(2)C5H3N) established a high-spin ferrous center ligated by a neutral bis(imino) pyridine ligand. Comparing these data to those for the single electron reduction product, ((i)PrPDl)FeCl, again demonstrated a high-spin ferrous ion, but in this case the S-Fe = 2 metal center is antiferromagnetically coupled to a ligand-centered radical (S-L 1/2), accounting for the experimentally observed S = 3/2 ground state. Continued reduction to ((PrPDI)-Pr-i)FeLn (L = N-2, n = 1,2; CO, n = 2; 4-(N,N-dimethylamino)pyridine, n = 1) resulted in a doubly reduced bis(imino)pyridine diradical, preserving the ferrous ion. Both the computational and the experimental data for the N,N-(dimethylamino)pyridine compound demonstrate nearly isoenergetic singlet (S-L = 0) and triplet (S-L = 1) forms of the bis(imino)pyridine dianion. In both spin states, the iron is intermediate spin (S-Fe = 1) ferrous. Experimentally, the compound has a spin singlet ground state (S = 0) due to antiferromagnetic coupling of iron and the ligand triplet state. Mixing of the singlet diradical excited state with the triplet ground state of the ligand via spin-orbit coupling results in temperature-independent paramagnetism and accounts for the large dispersion in H-1 NMR chemical shifts observed for the in-plane protons on the chelate. Overall, these studies establish that reduction of ((i)PrPDl)FeCl2 with alkali metal or borohydride reagents results in sequential electron transfers to the conjugated pi-system of the ligand rather than to the metal center.