A Terminal Iron(IV) Nitride Supported by a Super Bulky Guanidinate Ligand and Examination of Its Electronic Structure and Reactivity
A Terminal Iron(IV) Nitride Supported by a Super Bulky Guanidinate Ligand and Examination of Its Electronic Structure and Reactivity
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DOI：
10.1021/jacs.7b06919
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发表时间：
2017-11-08
影响因子：
15
通讯作者：
Fortier, Skye
中科院分区：
文献类型：
--
作者：
Maity, Arnab K.;Murillo, Jesse;Fortier, Skye
报道了利用体积较大的胍类配体[L-Ar*](-)(L-Ar*=(Ar*N)(2)C(R)，Ar*=2，6-二(二苯甲基)-4-叔丁基苯基，R=(NCBu2)-Bu-t)作为动力学稳定剂，合成了一种稀有端基Fe(IV)氮化物配合物。在0℃紫外光照射叠氮铁[L-Ar*]FeN3(Py)(3-py)的吡啶溶液，生成氮化铁[L-Ar*]Fen(Py)(1)。1(15N)(50%FO N-15)同位素的N-15核磁共振谱在1016ppm处有共振(与外部参考的CH3NO2在380ppm处相比)，与其他末端氮化铁的已知结果相当。值得注意的是，1的计算结构揭示了具有扭曲的四面体几何构型的铁中心，tau(4)=0.72，具有短的Fe N键(1.52埃)。对1的前线轨道有序性的考察表明，与由Fe(d(xz，yz))N(p(x，y))pi*-轨道组成的LUMO有较小的HOMO/LUMO距离，这种分裂表现在1的电子吸收光谱中(波长=610 nm，ε=1375 L中心点摩尔(-1)中心点厘米(-1)；波长=613run(Calcd))。配合物1在低温的吡啶溶液中持续存在，但在室温下变得不稳定，通过分子内N原子插入作用逐渐转化为Fe(II)酰肼产物[kappa(2)-((Bu2CN)-Bu-t)C(eta(6)-NAr*)(N-NAr*)]Fe(4)。通过分子轨道分析评价了Fe-N部分的反应活性，表明氮化物官能团具有亲电性。相应地，1与亲核剂PMe2Ph和Ar-NC(Ar=2，6-二甲基苯基)反应导致部分N原子转移并形成Fe(II)加成产物[L-Ar*]Fe(N=PMe2Ph)(Py)(5)和[L-Ar*]Fe(N=C=NaR)(Py)(6)。类似地，1与PhSiH3反应得到[L-Ar*]Fe[N(H)(SiH2Ph)](Py)(7)，Fukui分析表明该反应是通过将氮化物亲电插入到Si-H键中进行的。
Utilizing the bulky guanidinate ligand [L-Ar*](-) (L-Ar* = (Ar*N)(2)C(R), Ar* = 2,6-bis(diphenylmethyl)-4-tert-butylphenyl, R = (NCBu2)-Bu-t) for kinetic stabilization, the synthesis of a rare terminal Fe(IV) nitride complex is reported. UV irradiation of a pyridine solution of the Fe(II) azide [L-Ar*]FeN3(py) (3-py) at 0 degrees C cleanly generates the Fe(IV) nitride [L-Ar*]FeN(py) (1). The N-15 NMR spectrum of the 1(15N) (50% FO N-15) isotopomer shows a resonance at 1016 ppm (vs externally referenced CH3NO2 at 380 ppm), comparable to that known for other terminal iron nitrides. Notably, the computed structure of 1 reveals an iron center with distorted tetrahedral geometry, tau(4) = 0.72, featuring a short Fe N bond (1.52 angstrom). Inspection of the frontier orbital ordering of 1 shows a relatively small HOMO/LUMO gap with the LUMO comprised by Fe(d(xz,yz))N(p(x,y)) pi*-orbitals, a splitting that is manifested in the electronic absorption spectrum of 1 (lambda = 610 nm, epsilon = 1375 L center dot mol(-1)center dot cm(-1); lambda = 613 run (calcd)). Complex 1 persists in low-temperature solutions of pyridine but becomes unstable at room temperature, gradually converting to the Fe(II) hydrazide product [kappa(2)-((Bu2CN)-Bu-t)C(eta(6)-NAr*)(N-NAr*)]Fe (4) upon standing via intramolecular N-atom insertion. This reactivity of the Fe N moiety was assessed through molecular orbital analysis, which suggests electrophilic character at the nitride functionality. Accordingly, treatment of 1 with the nucleophiles PMe2Ph and Ar-N C (Ar = 2,6-dimethylphenyl) leads to partial N-atom transfer and formation of the Fe(II) addition products [L-Ar*]Fe(N=PMe2Ph)(py) (5) and [L-Ar*]Fe(N=C=NAr)(py) (6). Similarly, 1 reacts with PhSiH3 to give [L-Ar*]Fe[N(H)(SiH2Ph)](py) (7) which Fukui analysis shows to proceed via electrophilic insertion of the nitride into the Si-H bond.