Addition of Halocarboxylic Acids Esters and Halohydrocarbons to Pentafluorobenzaldehyde Promoted by Iron Pentacarbonyl

Iron pentacarbonyl is an efficient promoter of addition to the carbonyl group of pentafluorobenzene of alkyl α-halocarboxylates and alkyl halides. The electron-acceptor character of the pentafluorophenyl group essentially affects the course of reaction and the nature of the arising products.     

Photochemical reactions of 1-ferrocenyl-4-phenyl-1,3-butadiyne with Fe(CO)5 and CO

Photolysis of a hexane solution containing ironpentacarbonyl, 1-ferrocenyl-4-phenyl-1,3-butadiyne at low temperature yields six new products: [Fe(CO)₂{η²:η²-PhCCCC(Fc)C(CCPh)C(Fc)Fe(CO)₃}-μ-CO] (1), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-PhCCCC(Fc)-C(O)-C(Fc)CCCPh}] (2), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-FcCC(CC Ph)-C(O)-C(Fc)CCCPh}] (3), [Fe₂(CO)₆{μ-η¹:η¹:η²:η²-FcCCCC(Fc)-C(O)-C(Fc)CCCPh}] (4), [Fe(CO)₃{μ-η²: η²-[FcCC(CCPh)C(CCPh)C(Fc)}CO] (5) and [Fe(CO)₃{μ-η²: η²-[FcCC(CCPh)C(CCPh)C(Fc)}CO] (6) formed by coupling of acetylenic moieties with CO insertion on metal carbonyl support. In presence of CO, formation of another new product 2,5-bis(ferrocenyl)-3,6-bis(tetracarbonylphenylmaleoyliron)quinone (7) was observed which on further reaction with ferrocenylacetyene gave the quinone, 2,5-bis(ferrocenyl)-3,6-bis(ethynylphenyl)quinone (8). Structures of 1-5 and 8 were established crystallographically.     

Ligand-Free Synthesis of 1,4-Disubstituted-1,3-diynes by Iron/Copper Cocatalyzed Homocoupling of Terminal Alkynes

A simple and efficient protocol for Fe/Cu cocatalyzed oxidative homocoupling reaction of terminal alkynes to symmetrical 1,4‐disubstituted‐1,3‐diynes was presented. The results showed that both CuBr and FeCl₃ played crucial roles in the reaction. It is noteworthy that this protocol employs mild, efficient, aerobic and ligand free conditions. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed into the corresponding 1,3‐diynes in good to excellent yields.     

Addition of α-Halo-substituted Carbonitriles to and AldehydesKetones in the Presence of Iron Pentacarbonyl

Halo-substituted carbonitriles in the presence of iron pentacarbonyl react with aldehydes and ketones by Reformatsky reaction type. In contract to halo-substituted esters the nitriles are considerably more reactive toward ketones than aldehydes. At the same time the structure and yield of products obtained from both nitriles and esters are strongly and similarly affected by the character of the para-substituents in the benzaldehyde.     

碳锗双桥连二环戊二烯与羰基铁的反应

碳锗双桥连二环戊二烯(Me₂C)(Me₂Ge)(C₅H₄)₂(1)与五羰基铁在回流甲苯及二甲苯中的反应,得到正常的Fe-Fe键化合物(Me₂C)(Me₂Ge)[(η⁵-C₅H₃)Fe(CO)]₂(μ-CO)₂(3)和脱锗桥产物(Me₂C)[(η⁵-C₅H₄)Fe(CO)]₂(μ-CO)₂(4)以及一个结构新颖的化合物(Me₂C)[(η⁵-C₅H₃)[(Me₂Ge)Fe(CO)₂](η¹,η⁵-C₅H₃)[Fe(CO)₂](2).用X射线衍射分析測定了化合物3的晶体结构,并提出了可能的生成机理.     

The synthesis and electrochemical behavior of 1,4-di-(2,5-dimethylazaferrocenyl)-1,3-butadiyne

Rigid-rod ferrocene capped alkynes have attracted a lot of attention recently. In this note we report an efficient synthesis of the 1,4-di-(2,5-dimethylazaferrocenyl)-1,3-butadiyne which is the first known azaferrocene capped diacetylene derivative. The cyclic voltammetry measurements at different scan rates and temperatures indicate good electronic communication between two iron centers. Better shaped reduction peaks at higher scan rates in 22 °C and −40 °C can point to increased stability of the monocation.     

The Flipping of CO Ligand Groups in Metal Carbonyl Compounds and its Frequency in Fe(CO)5

It has been proven qualitatively by a number of authors using variable temperature NMR experiments that most metal carbonyl complexes are nonrigid. A quantitative determination of the ligand exchange frequency v_e is often achieved by a line shape analysis or by measurement of the transverse relaxation time T₂ using the Carr-Purcell method. In the case of a “very fast” exchange, however, both methods prove unsuccessful. It is shown in this study that a simultaneous fit of IR or Raman spectra on the one hand and NMR spectra on the other can make possible the determination of v_e for the “very fast” exchange and can also facilitate the determination of v_e in “slow” and “medium” exchange cases considerably. The ligand exchange frequency thus found for Fe(CO)₅, 1.1 × 10¹⁰s^?1, is unexpectedly high; comparison with variable temperature measurements on solid Fe(CO)₅, yields similar energy barriers. A mechanism of exchange closely related to the “Berry mechanism” is proposed. Finally the consequences of this surprisingly large ligand exchange rate are discussed with respect to IR band assignments for molecular “fragments” M(CO)^x (where x=coordination number, and M is a transition metal, typically lanthanoid or actinoid).     

Reaction Behavior of Decacarbonyldimetalates(2‐) (M = Cr and Mo) towards the Nitrosyl Carbonyls of Iron and Cobalt

The reaction of the nitrosyl carbonyl complexes [Fe(NO)₂(CO)₂] and [Co(NO)(CO)₃] with the decacarbonyldimetalates [M₂(CO)₁₀]^2– (M = Cr and Mo) in THF as the solvent at room temperature was investigated. Thereby a substitution of one nitrosyl ligand towards carbon monoxide was observed in each case. Both reactions afforded the known metalate complexes [Fe(NO)(CO)₃]^– and [Co(CO)₄]^–, respectively. These species were isolated as their corresponding PPN salts [PPN⁺ = bis(triphenylphosphane)iminium cation] in nearly quantitative yields. The products were unambiguously identified by their IR spectroscopic and elemental analytic data as well as by their characteristic colors and melting points.     

Addition of aluminum and gallium species to aromatic and alkyl-substituted 1,4-diaza-1,3-butadiene ligands

In this report, we investigate the interactions of Me(x)MCl(3-x) (x = 0-3, M = Al, Ga) with various aromatic and alkyl-substituted 1,4-diaza-1,3-butadiene (R)DAB ligands (or α-diimine ligands) to give a variety of structures in solution and in the solid state. In combination with other previously reported structures, certain general trends of reactivity of these species can be deduced, although there are still some unexplained modes of reactivity. The methylated Al species react with aromatic-substituted (R)DAB ligands to provide final products that result from C═N insertion into the Al-CH(3) group followed by rearrangement reactions. The addition of methyl groups onto the backbone of the (R)DAB ligand is insufficient to stop the insertion and rearrangement processes from occurring. In the case of MeAlCl(2) with the bulky (DiPP)DAB ligand, the reaction could be followed spectroscopically from the monoadduct through the inserted/rearranged final product. Methylated Ga species, however, are much less predictable in their behavior with aromatic-substituted (R)DAB ligands. Depending on the exact species and ratios used, coordinated adducts can be formed and identified, or inserted/rearranged products similar to the aluminum reactions can be obtained. Quite interestingly, cation/anion pairs can also be formed in which GaCl(3) or MeGaCl(2) act as a chloride acceptors. This behavior was unique and substantially different from the analogous Al reactions which formed either a dicoordinated adduct or an inserted/rearranged complex. When the stronger-donating alkyl-substituted (R)DAB ligands were used with Me(2)GaCl, only cation/anion pairs were obtained. Surprisingly, when the same reactions were performed using Me(2)AlCl as a reagent, irreproducible results were obtained.     

氧化铁磁性纳米粒子的表面配体交换及相转移

以苯甲醇为单一溶剂, 通过常压、高温热解乙酰丙酮铁, 制备了尺寸单分散的四氧化三铁磁性纳米粒子. 采用透射电镜(TEM), X射线衍射(XRD), 动态光散射(DLS)等方法对粒子形貌和结构进行了表征. 利用傅里叶变换红外(FT-IR)光谱和热重分析(TGA)研究了所制备纳米粒子的表面化学, 结果表明稳定四氧化三铁粒子的是苯甲酸分子, 且表面覆盖度小于20%. 所制备的磁性纳米粒子可以在室温下方便地进行表面配体交换, 从而为氧化铁磁性纳米粒子的功能化提供新的途径.     

The Coordination Chemistry of Iron with the 1,4‐Bis(2‐pyridyl‐methyl)piperazine Ligand

The behaviour of Fe^II and Fe^III ions in combination with the potential ligand 1,4‐bis(2‐pyridyl‐methyl)piperazine (BPMP) under anhydrous conditions has been investigated. BPMP has been reacted with FeCl₂, FeCl₃ and [Fe(OTf)₂(MeCN)₂]. This led to the isolation of four new complexes, which were fully characterized and structurally investigated by single crystal X‐ray diffraction. It turned out that in the presence of chloride co‐ligands Fe^III favours the tetradentate coordination mode of BPMP with the piperazine unit in a boat configuration, like for instance in [BPMP(Cl)Fe(μ‐O)FeCl₃] or [BPMP‐FeCl₂][FeCl₄], ( 1 ). However, the employment of FeCl₂ leads to the formation of a coordination polymer [BPMP‐FeCl₂]_n, ( 2 ), containing the piperazine ring in a chair configuration binding to two iron centres each. 2 can only be dissolved in very polar solvents like dmf which is capable of breaking up the polymeric structure under formation of [Cl₂(dmf)Fe(μ‐BPMP‐1κ²N,N:2κ²N,N))Fe(dmf)Cl₂]·2 dmf, ( 3 ). In contrast, using [Fe(OTf)₂(MeCN)₂] instead of FeCl₂ as the starting material leads to a mononuclear Fe^II complex with BPMP bound in the desirable tetradentate fashion: [BPMP‐Fe(OTf)₂], ( 4 ). Unlike other complexes with tetradentate N/py ligands the two residual ligands in 4 are bound almost trans to each other with the potential to adopt a cis orientation under oxidising conditions, and it will be interesting to exploit its catalytic properties in future.     

Formation of Iron Macro-Spheres in Plasma

In this paper the formation mechanism of iron macro-spheres in a plasma medium is dealt with, including the conditions under which such spheres are formed. The geometry of the spheres referred to above depends on the main technological parameters involved in the production of pores. Conditions under which pores occur within macro-spheres are also established. The radii of these pores are sensitive to the velocity distribution within the plasma jet section     

Synthesis and Characterization of a Novel Phenol‐tailed Porphyrin Ligand and Its Iron(III) Complex

The phenol‐tailed porphyrin ligand, H₃L was synthesized as a model compound for catalases. H₃L and its corresponding iron complex [Fe(L)] were synthesized by using the precursor, 5‐(8‐ethoxycarbonyl‐1‐naphthyl)‐10, 15, 20‐triphenyl porphyrin (ENTPP). They were characterized by ¹H NMR spectroscopy, mass spectrometry, X‐ray crystallography, and cyclic voltammetry. All the results have confirmed that the phenol group is covalently attached to the porphyrin. In the iron complex, phenolate oxygen is coordinated to iron(III) as the fifth ligand, leading to the five‐coordinate high‐spin iron(III) species.     

碳纳米管封装铁纳米粒子催化剂上CO加氢制低碳烯烃

由于石油资源的逐步枯竭,近年来费托(F-T)反应因其可以高效将煤、天然气和生物质等转化成液体燃料和高值化学品而越来越受到人们的关注。相比于Co, Ni和Ru等F-T催化剂, Fe基催化剂因其价格低廉,产物分布广而被广泛研究。以合成气直接制备低碳烯烃的F-T过程为例,铁基催化剂通常会因积碳和烧结的问题,而导致失活。因此,人们通常使用一些氧化物载体,比如氧化硅,氧化铝或者分子筛来分散并稳定铁粒子。但是这类氧化物载体通常与铁有非常强的相互作用,特别是在铁粒子较小的情况下,容易生成一些难于还原的硅酸铁和铝酸铁。而活性炭、碳纤维等惰性载体与铁的相互作用较弱,不足以稳定小的铁粒子在而反应过程中聚集。近来,我们组提出了利用石墨烯碳层封装过渡金属粒子作为催化剂,利用“穿透”的金属电子来催化反应,从而可以使活性中心和反应介质隔离,有效地增强了非贵金属催化剂的活性和稳定性。在此基础上,我们组和其他课题组的研究表明,一系列石墨烯碳层封装的非贵金属催化剂在燃料电池阴极氧还原反应,电催化析氢反应,染料敏化太阳能电池中的I3–还原反应以及催化氧化还原反应中都有着广泛的应用前景。这种材料中碳层不仅能在氧化气氛、酸性介质中保护包覆的金属,防止其被氧化或者腐蚀,还与包覆的金属有着较强的相互作用,可以促进非贵金属的电子向碳层表面的转移,有望在一些苛刻的反应条件下实现对贵金属催化剂的替代。本文进一步拓展了其在高温反应中的应用,发现豆荚状碳纳米管封装的金属铁纳米粒子在合成气制备低碳烯烃中可以有效防止金属铁纳米粒子的烧结和聚集,因此表现出优异的低碳烯烃选择性和催化稳定性。我们利用一步化学反应法合成了豆荚状碳纳米管封装的铁纳米粒子催化剂(Pod-Fe),并通过酸洗除去碳管外面裸露的铁粒子。透射电镜(TEM)和X射线衍射(XRD)表明酸洗后铁粒子被包覆在碳管内,并且呈金属态,而酸洗前,则还有大量的氧化铁粒子分布于碳管外部(FeOx/Pod-Fe)。将酸洗前后的两个催化剂用于固定床气相F-T反应中。通过调节空速和温度考察了它们的催化反应性能,结果表明两个催化剂在不同的反应条件下都有着良好的低碳烯烃选择性。不同反应温度下,它们表现出不同的变化趋势：Pod-Fe活性随着温度的升高而缓慢增长,至380 oC都没有明显的失活现象;而对于FeOx/Pod-Fe催化剂,随着温度的升高, CO的转化率先升高,在300 oC时达最高,但随着温度进一步升高,活性迅速降低,呈现一个火山型曲线。 TEM结果发现,反应后FeOx/Pod-Fe催化剂粒子上产生了很多杂乱的碳丝,并且铁粒子有着明显的聚集长大。而Pod–Fe催化剂即使在380 oC反应后,其形貌仍然保持完好,没有积碳产生,粒子也没有发生聚集和长大。进一步在320 oC下120 h的寿命试验发现, Pod-Fe催化剂的初始活性较低,但经20 h的活化阶段,活性会先增加后略有下降,20 h后趋于稳定。而FeOx/Pod-Fe催化剂在反应初始虽然表现出较高的活性,但是随着时间进行,活性迅速下降一半以上,最后趋于稳定。同时结合反应后TEM和XRD的结果发现碳管外部裸露的铁粒子会在反应过程中形成碳化铁物种,并随着反应进行产生聚集,并伴有大量积碳,导致活性迅速下降;而碳层的包覆对于铁粒子有着很好的稳定作用,使得铁粒子能够在高温反应中保持稳定,并且没有积碳的产生。由此可见石墨烯碳层可以有效保护其包覆的金属粒子,并且能够提高其在高温反应下的低碳烯烃选择性和稳定性。此类催化剂有望在一些苛刻条件下的多相催化反应中得到广泛应用。     

Iron pentacarbonyl assisted photochemical route to 2,5- and 2,6-divinyl-substituted 1,4-benzoquinones from 1-ene-3-ynes

Photochemical reaction between the enynes, (Z)-1-methoxybut-1-ene-3-yne, 1 or isopropenyl acetylene, 2 with CO in presence of Fe(CO)₅ yields the 2,6- and 2,5-divinyl-substituted 1,4-benzoquinones: 2,6-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (3, 42%), 2,5-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (4, 31.5%), [{η²,η²:2,6-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (5, 45%), and {η²,η²:2,5-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (6, 65%).     

Synthesis of 3-Acyl and 3-Carboalkoxyfurans by the Ceric Ammonium Nitrate Promoted Addition of 1,3-Dicarbonyl Compounds to Vinylic Acetates

3-Acyl- and 3-carboalkoxyfurans can be prepared in 30–55% yield by the oxidative addition of 1,3-dicarbonyl compounds to vinylic acetates induced by eerie ammonium nitrate.     

A Simple Test to Confirm the Ligand Substitution Reactions of the Hydrolytic Iron(iii) Dimer

Using a novel test method based on initial rates, periodate, dithionate, selenite, phosphite, hypophosphite, and arsenate ions were confirmed to form transient multinuclear iron(III) complexes directly with the iron(III) hydroxo dimer Fe₂ (OH)₂ (H₂ O)8     

Structure and Reactivity of Iron(0)-Phenyltellurolate [PPN][PhTeFe(CO)4]

Anionic iron(0) tetracarbonyl with terminal phenyltellurolate ligand PhTe^?, [PhTeFe(CO)₄]^?, has been synthesized and characterized. The title compound was obtained by addition of (PhTe)₂ to [PPN][HFe(CO)₄] THF solution dropwise. [PPN][PhTeFe(CO)₄] crystallizes in the monoclinic space group C c, with a = 16.119(4) Å, b = 13.141(3) Å, c = 19.880(8) Å, β = 93.04(3)°, V = 4205(2) ų, and Z = 4. The [PhTeFe(CO)₄]^? anion is a trigonal-bipyramidal complex in which the phenyltellurolate ligand occupies an axial position with Fe-Te bond length 2.630(5) Å and the Fe-Te-C(Ph) angle is 103.4(5)°. The neutral iron(0)-telluroether compound, (PhTeMe)Fe(CO)₄, was prepared by alkylation of the [PhTeFe(CO)₄]^?. Protonation of [PhTeFe(CO)₄]^?and reaction of H₂Fe(CO)₄ and PhTe)₂ ultimately lead to formation of the known dimer Fe₂(μ-TePh)₂(CO)₆ and H₂.