Reactivity studies on [Cp'FeI]2: monomeric amido, phenoxo, and alkyl complexes.
Reactivity studies on [Cp'FeI]2: monomeric amido, phenoxo, and alkyl complexes.
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DOI：
10.1021/ic301770f
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发表时间：
2012-10
影响因子：
4.6
通讯作者：
Marc D. Walter;P. White
中科院分区：
文献类型：
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作者：
Marc D. Walter;P. White
合成了一系列单体单（环戊二烯基）铁胺、苯氧基和烷基配合物，并介绍了它们的结构和反应活性。这些14VE单脚钢琴凳配合物的铁（II）中心在固态和溶液中具有高自旋（S = 2），与溶剂无关。硅酰胺化合物[Cp' fen (SiMe(3))(2)] (2a, Cp' = 1,2,4-(Me(3)C)(3)C（5)H(2)）是与较酸性底物（如酚）反应的优良起始材料。研究了2,6-(Me(3)C)(2)(4-R)C(6)H(2)OH （R = H, Me，和tBu）立体负担苯酚。在所有情况下，单体铁-苯氧基半夹层配合物[Cp' feor '] （4-R）最初形成。在2,6-(Me(3)C)(2)(4-R)C(6)H(2) R'(2)R ')OH （R = H和Me）中观察到4-R向抗磁性氧环己二烯基络合物[Cp' fe (η(5)- o = C(6)H(2)R'))] （5-R）的重排，并测定了吉布斯自由活化焓（ΔG（‡））。相反，当4位被tBu基团阻断时，这种重排被抑制。除去2,6位上的空间块，形成μ-苯氧基二聚体[Cp'Fe(μ-OC(6)H(3)tBu(2)-3,5)](2)(5)。利用密度泛函理论（DFT）进一步阐明了这些分子的结构-反应性关系。单腿钢琴凳苯胺配合物[Cp'Fe(NHC(6)H(2)tBu(3)-2,4,6)](7)不能通过2a和H(2)NC(6)H（2)tBu(3)-2,4,6）的酸碱反应得到，但可以通过[Cp'FeI](2)和[Li(NHC(6)H(2)tBu(3)-2,4,6)(OEt(2))](2)的常规盐分解反应得到。相反，2a与Ph(2) nhh反应生成双金属[Cp'Fe(N,C-κ(1),η(5)-C(6)H(5)NPh)Fe(N-κ(1)-NPh(2))Cp'](8)，它结合了两个铁中心，具有相同的氧化态（+2），但不同的自旋态（S = 0和S = 2），这反映在Cp(cent)-Fe距离分别为1.68和2.04 Å。制备了一种对H(2)、C(2)、H(4)和N(2)O无反应的单体烷基铁半夹心配合物[Cp'FeCH(SiMe(3))(2)](9)。这种行为可能被自旋态诱导的反应势垒合理化。然而，9在CO存在下与铁酰基络合物[Cp'Fe(CO)(2)(C(O)CH(SiMe(3))(2))]（10）发生反应，并与CO/H(2)混合物[Cp'Fe(CO)(2)](2)（11）和CH(2)(SiMe(3))(2)形成。
A series of monomeric mono(cyclopentadienyl) iron amido, phenoxo, and alkyl complexes were synthesized, and their structure and reactivity are presented. The iron(II) centers in these 14VE one-legged piano stool complexes are high spin (S = 2) in solid state and solution independent of solvent. The silylamide compound [Cp'FeN(SiMe(3))(2)] (2a, Cp' = 1,2,4-(Me(3)C)(3)C(5)H(2)) is an excellent starting material for the reaction with more acidic substrates such as phenols. Sterically encumbered phenols 2,6-(Me(3)C)(2)(4-R)C(6)H(2)OH (R = H, Me, and tBu) were investigated. In all cases monomeric iron phenoxo half-sandwich complexes [Cp'FeOR'] (4-R) are initially formed. Rearrangement of 4-R to the diamagnetic oxocyclohexadienyl complex [Cp'Fe(η(5)-O═C(6)H(2)R'(2)R")] (5-R) is observed for 2,6-(Me(3)C)(2)(4-R)C(6)H(2)OH (R = H and Me) and the Gibbs free enthalpy of activation (ΔG(‡)) was determined. In contrast this rearrangement is inhibited when the 4-position is blocked by a tBu group. Removing the steric bulk from the 2,6-positions leads to the formation of a μ-phenoxo dimer, [Cp'Fe(μ-OC(6)H(3)tBu(2)-3,5)](2) (5). Density functional theory (DFT) was used to further elucidate the structure-reactivity relationship in these molecules. The one-legged piano stool anilido complex [Cp'Fe(NHC(6)H(2)tBu(3)-2,4,6)] (7) is not accessible via acid-base reaction between 2a and H(2)NC(6)H(2)tBu(3)-2,4,6, but can be prepared by conventional salt metathesis reaction from [Cp'FeI](2) and [Li(NHC(6)H(2)tBu(3)-2,4,6)(OEt(2))](2). In contrast, reaction of 2a with Ph(2)NH yields the bimetallic [Cp'Fe(N,C-κ(1),η(5)-C(6)H(5)NPh)Fe(N-κ(1)-NPh(2))Cp'] (8) which combines two iron centers in the same oxidation state (+2), but different spin-states (S = 0 and S = 2) which is reflected in very different Cp(cent)-Fe distances of 1.68 and 2.04 Å, respectively. A monomeric iron alkyl half-sandwich complex [Cp'FeCH(SiMe(3))(2)] (9) was prepared that exhibits no reactivity toward H(2), C(2)H(4) or N(2)O. This behavior might be rationalized by a spin-state induced reaction barrier. However, 9 reacts in the presence of CO to the iron acyl-complex [Cp'Fe(CO)(2)(C(O)CH(SiMe(3))(2))] (10) and with a CO/H(2) mixture [Cp'Fe(CO)(2)](2) (11) and CH(2)(SiMe(3))(2) are formed.