Die in dieser Publikation behandelten Themen sollen viele verschiedene Aspekte der Chemie vermitteln, die einen guten & Uuml;berblick & uuml;ber die grundlegenden Kenntnisse der anorganischen Chemie geben und den gr & ouml;ss ten Teil einer Erstsemestervorlesung abdecken sollen. Dennoch geht das vermittelte Wissen weit & uuml;ber das Verst & auml;ndnis grundlegender Redox- oder S & auml;ure-Base-Reaktionen hinaus. Das Demonstrieren von Versuchen geht immer Hand in Hand mit der Vermittlung des richtigen und sicheren Umgangs mit Chemikalien. In vielen dieser Experimente wurden Chemikalien verwendet, die mit & auml;u ss erster Sorgfalt behandelt werden m & uuml;ssen. Ein Chemiker muss sich immer & uuml;ber die Gefahren im Klaren sein, die mit bestimmten Chemikalien verbunden sind. Stoffe, die stark mit Wasser, Luft oder mit chlorierten L & ouml;sungsmitteln reagieren, m & uuml;ssen immer unter den richtigen Bedingungen gehandhabt werden. Alle gezeigten Experimente sind kontrollierte Explosionen und Verbrennungen. Es w & auml;re schrecklich, sich vorzustellen, welche Sch & auml;den durch Fehlkalkulationen und falsche Anwendung entstehen k & ouml;nnen. Diese Arbeit sollte auch als Mahnung verstanden werden, Chemikalien mit dem n & ouml;tigen Respekt, aber niemals mit Angst zu behandeln. Schlie ss lich sind chemische Reaktionen das t & auml;gliche Gesch & auml;ft fast aller Chemiker. Die Erkenntnisse und Erfahrungen, die man durch die Lekt & uuml;re dieses Artikels oder durch das Anschauen von Videos zu diesen chemischen Experimenten gewinnt, k & ouml;nnen gegebenenfalls den Unterricht im H & ouml;rsaal bereichern, aber sie k & ouml;nnen niemals das Gef & uuml;hl eines Live-Experiments ersetzen. The topics addressed in this publication should have taught many different aspects of chemistry, providing a good overview of the fundamental knowledge of inorganic chemistry and covering the major part of a first-semester lecture. Still, the knowledge transferred goes far beyond the understanding of basic redox or acid-base reactions. Demonstrating experiments always goes hand in hand with teaching the correct and safe handling of chemicals. In many of these experiments, chemicals were used that must be treated with extreme care. A chemist should always be aware of the dangers associated with specific chemicals. Substances that react vigorously with water, in air, or with chlorinated solvents must always be handled under the right conditions. All demonstrated experiments involved controlled explosions and combustions. It would be dreadful to imagine the damage resulting from miscalculations and improper use. This work should also serve as a reminder to treat chemicals with the appropriate respect, but never with fear. In the end, chemical reactions are the everyday business of nearly every chemist. The experience and knowledge gained from reading this text or watching a movie about one of these chemical experiments can enhance classroom teaching, if necessary, but can never replace the feeling of a live performance experiment.

As key intermediates in metal-catalyzed nitrogen-transfer chemistry, terminal imido complexes of iron have attracted significant attention for a long time. In search of versatile model compounds, the recently developed second-generation N-anchored tris-NHC chelating ligand tris-[2-(3-mesityl-imidazole-2-ylidene)-methyl]amine (TIMMNMes) was utilized to synthesize and compare two series of mid- to high-valent iron alkyl imido complexes, including a reactive Fe(V) adamantyl imido intermediate en route to an isolable Fe(V) nitrido complex. The chemistry toward the iron adamantyl imides was achieved by reacting the Fe(I) precursor [(TIMMNMes)FeI(N2)]+ (1) with 1-adamantyl azide to yield the corresponding trivalent iron imide. Stepwise chemical reduction and oxidation lead to the isostructural series of low-spin [(TIMMNMes)Fe(NAd)]0,1+,2+,3+ (2Ad-5Ad) in oxidation states II to V. The Fe(V) imide [(TIMMNMes)Fe(NAd)]3+ (5Ad) is unstable under ambient conditions and converts to the air-stable nitride [(TIMMNMes)FeV(N)]2+ (6) via N-C bond cleavage. The stability of the pentavalent imide can be increased by derivatizing the nitride [(TIMMNMes)FeIV(N)]+ (7) with an ethyl group using the triethyloxonium salt Et3OPF6. This gives access to the analogous series of ethyl imides [(TIMMNMes)Fe(NEt)]0,1+,2+,3+ (2Et-5Et), including the stable Fe(V) ethyl imide. Iron imido complexes exist in a manifold of different electronic structures, ultimately controlling their diverse reactivities. Accordingly, these complexes were characterized by single-crystal X-ray diffraction analyses, SQUID magnetization, and electrochemical methods, as well as 57Fe Mössbauer, IR vibrational, UV/vis electronic absorption, multinuclear NMR, X-band EPR, and X-ray absorption spectroscopy. Our studies are complemented with quantum chemical calculations, thus providing further insight into the electronic structures of all complexes.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A new supporting ligand, tris-[2-(3-mesityl-imidazol-2-ylidene)methyl]amine (TIMMNMes), was developed and utilized to isolate an air-stable iron(V) complex bearing a terminal nitrido ligand, which was synthesized by one-electron oxidation from the iron(IV) precursor. Single-crystal X-ray diffraction analyses of both complexes reveal that the metal-centered oxidation is escorted by iron nitride (Fe≡N) bond elongation, which in turn is accompanied by the accommodation of the high-valence iron center closer to the equatorial plane of a trigonal bipyramid. This contrasts with the previous observation of the only other literature-known Fe(IV)≡N/Fe(V)≡N redox pair, namely, [PhB(tBuIm)3FeN]0/+. On the basis of 57Fe Mössbauer, EPR, and UV/vis electronic absorption spectroscopy as well as quantum chemical calculations, we identified the lesser degree of pyramidalization around the iron atom, the Jahn-Teller distortion, and the resulting nature of the SOMO to be the decisive factors at play.

AbstractThe facile synthesis of the first bis‐N‐heterocyclic imine‐stabilized chlorosilyliumylidene 1 is reported. Remarkably, consecutive reaction of 1 with PPh3AuCl and K2Fe(CO)4 gives rise to the unique heterobimetallic complex 1,2‐(MesNHI)2‐C2H4‐ClSiAuFe(CO)4 (4). The overall neutral complex 4 bears an unusual linear Si−Au−Fe structure and a rare anagostic interaction between the d10‐configured gold atom and a CH bond of the mesityl ligand. According to the computational analysis and 57Fe Mössbauer spectroscopy, the formal Fe‐oxidation state remains at −II. Thus, the electronic structure of 4 is best described as an overall neutral—yet zwitterionic—heterobimetallic “Si(II)+‐Au(I)+‐Fe(‐II)2−”‐silyliumylidene complex, derived from double anion exchange. The computational analysis indicates strong hyperconjugative back donation from the gold(I) atom to the silyliumylidene ligand.

Iron-nitrosyls have fascinated chemists for a long time due to the noninnocent nature of the NO ligand that can exist in up to five different oxidation and spin states. Coordination to an open-shell iron center leads to complex electronic structures, which is the reason Enemark-Feltham introduced the {Fe-NO}n notation. In this work, we succeeded in characterizing a series of {Fe-NO}6-9 complexes, including a reactive {Fe-NO}10 intermediate. All complexes were synthesized with the tris-N-heterocyclic carbene ligand tris[2-(3-mesitylimidazol-2-ylidene)ethyl]amine (TIMENMes), which is known to support iron in high and low oxidation states. Reaction of NOBF4 with [(TIMENMes)Fe]2+ resulted in formation of the {Fe-NO}6 compound [(TIMENMes)Fe(NO)(CH3CN)](BF4)3 (1). Stepwise chemical reduction with Zn, Mg, and Na/Hg leads to the isostructural series of high-spin iron nitrosyl complexes {Fe-NO}7,8,9 (2-4). Reduction of {Fe-NO}9 with Cs electride finally yields the highly reduced {Fe-NO}10 intermediate, key to formation of [Cs(crypt-222)][(TIMENMes)Fe(NO)], (5) featuring a metalacyclic [Fe-(NO-NHC)3-] nitrosoalkane unit. All complexes were characterized by single-crystal XRD analyses, temperature and field-dependent SQUID magnetization methods, as well as 57Fe Mössbauer, IR, UV/vis, multinuclear NMR, and dual-mode EPR spectroscopy. Spectroscopy-based DFT analyses provide insight into the electronic structures of all compounds and allowed assignments of oxidation states to iron and NO ligands. An alternative synthesis to the {Fe-NO}8 complex was found via oxygenation of the nitride complex [(TIMENMes)Fe(N)](BF4). Surprisingly, the resulting {Fe-NO}8 species is electronically and structural similar to the [(TIMENMes)Fe(N)]+ precursor. Based on the structural and electronic similarities between this nitrosyl/nitride complex couple, we adopted the strategy, developed by Wieghardt et al., of extending the Enemark-Feltham nomenclature to nitrido complexes, rendering [(TIMENMes)Fe(N)]+ as a {Fe-N}8 species.

Iron-Nitrosyls have fascinated chemists for a long time due to the non-innocent nature of the NO ligand that can exist in up to five different oxidation and spin states. Coordination to an open-shell iron center leads to complex electronic structures, which is the reason Enemark and Feltham introduced the {Fe-NO}n notation.1 In this work, we succeeded to characterize a series of {Fe-NO}6-9 complexes, including a reactive {Fe-NO}10 intermediate. All complexes were synthesized with the tris-N-heterocyclic carbene ligand tris[2-(3-mesityl-imidazol-2-ylidene)ethyl]amine (TIMENMes), which is known to support iron in high and low oxidation states. Reaction of NOBF4 with [(TIMENMes)Fe]2+ resulted in formation of the {Fe-NO}6 compound [(TIMENMes)Fe(NO)(CH3CN)](BF4)3, (1). Stepwise chemical reduction with Zn, Mg, and Na/Hg leads to the isostructural series of high-spin iron nitrosyl complexes {Fe-NO}7,8,9 (2 - 4). Reduction of {Fe-NO}9 with Cs electride finally yields the highly reduced {Fe-NO}10 intermediate, key to formation of [Cs[2.2.2.]crypt][(TIMENMes)Fe(NO)], (5) featuring a metalacyclic {Fe-NHC(NO)3-} nitrosoalkane unit. All complexes were characterized by single-crystal XRD analyses, temperature and field-dependent SQUID magnetization methods as well as 57Fe Mössbauer, IR, UV/vis, multi-nuclear NMR, and dual-mode EPR spectroscopy. Spectroscopy-based DFT analyses provide insight into the electronic structures of all compounds and allowed assignments of oxidation states to iron and NO ligands. An alternative synthesis to the {Fe-NO}8 complex was found via oxygenation of the nitride complex [(TIMENMes)Fe(N)](BF4). Surprisingly, the resulting {Fe-NO}8 species is electronically and structural similar to the [(TIMENMes)Fe(N)]+ precursor. Based on the structural and electronic similarities between this nitrosyl/nitride complex couple, we adopted the strategy, developed by Wieghardt et al.,1 of extending the Enemark & Feltham nomenclature to nitrido complexes, rendering [(TIMENMes)Fe(N)]+ as a {Fe-N}8 species.

The half-sandwich complex [Cp'Fe(μ-I)]2 (1; Cp' = η5-1,2,4-(Me3C)3C5H2) is cleaved when heated in toluene to form a cation-anion pair [{Cp'Fe(η6-toluene)}+{Cp'FeI2}-] (2), in which the two Fe(ii) atoms adopt different spin states, i.e., a low-spin (S = 0) and a high-spin (S = 2) configuration. Upon oxidation of 1 with C2H4I2, the thermally stable 15VE species [Cp'FeI2] (3) can be isolated, in which the Fe(iii) atom adopts an intermediate spin (S = 3/2) configuration. Complex 3 is an excellent starting material for further functionalizations and it reacts with Mg(CH2SiMe3)2 to form the unprecedented Fe(iii) (S = 3/2) bis(alkyl) complex [Cp'Fe(CH2SiMe3)2] (4). The respective spin states of complexes 2-4 are confirmed by single-crystal X-ray crystallography, zero-field 57Fe Mössbauer spectroscopy, and solid-state magnetic susceptibility measurements. In contrast to the related 14VE high-spin (S = 2) Fe(ii) alkyl species [Cp'FeCH(SiMe3)2], which resists the reaction with H2 as a consequence of a spin-induced reaction barrier, complex 4 reacts cleanly with H2 (8 bar) in cyclohexane to yield iron hydrides [{Cp'Fe}2(μ-H)3] (5) and [Cp'Fe(μ-H)2]2 (6) in a 1 : 4 ratio. However, when the hydrogenation of 4 is carried out in benzene, a green 19VE [Cp'Fe(η6-C6H6)] (A) intermediate is formed, which dimerizes to the bis(cyclohexadienyl)-bridged product [(Cp'Fe)2(μ2-η5:η5-C12H12)] (7). Further evidence for the intermediacy of [Cp'Fe(η6-C6H6)] (A) was gathered by X-band EPR and UV/vis spectroscopy. Interestingly, attempts to oxidize 7 with AgSbF6 proceeded via C-C bond cleavage instead of metal oxidation to form [Cp'Fe(C6H6)][SbF6] (8).

The first synthesized and X-ray structurally characterized "classical" iron(i) dioximate showed an unrivaled stability towards strong acids, thus calling for a reassessment of the origins of the electrocatalytic activity of similar low-valent cobalt and iron cage complexes with electron-withdrawing ribbed substituents, shown previously to be effective electrocatalysts of the HER.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The 16-valence electron species [Cp*2 Fe]2+ (Cp*=η-C5 Me5 ), formally featuring a tetravalent iron ion, quantitatively binds CO in HF solution to form the stable, diamagnetic carbonyl species [Cp*2 Fe(CO)]2+ . This dication forms salts in the presence of AsF6- and SbF6- that were crystallographically characterized. The molecular structure in crystals of [Cp*2 Fe(CO)](AsF6 )2 displays cyclopentadienyl rings that are clearly not parallel and an equatorially bound η1 -CO ligand. The formal oxidation state +IV of iron was investigated by 57 Fe Mössbauer spectroscopy and is supported by DFT computational analysis. A detailed spectroscopic characterization of the hitherto unprecedented high-valent iron carbonyl compounds is reported.

AbstractDer formale FeIV‐16‐Valenzelektronen‐Komplex [Cp*2Fe]2+ reagiert quantitativ mit CO in wasserfreiem HF zum stabilen, diamagnetischen Carbonylkomplex [Cp*2Fe(CO)]2+. Das Dikation bildet stabile Salze mit AsF6− und SbF6−, von denen erstere kristallographisch charakterisiert werden konnten. Die Molekülstruktur des Dikations in [Cp*2Fe(CO)](AsF6)2 weist einen äquatorial am Eisen gebundenen η1‐CO‐Liganden auf. Die Cp*‐Ringe stehen nicht parallel zueinander, sondern leicht schräg. Die Oxidationsstufe +IV wurde mittels 57Fe‐Mößbauer‐Spektroskopie und DFT‐Rechnungen nachgewiesen. Außerdem werden weitere spektroskopische Daten dieser neuartigen hochvalenten Eisencarbonylverbindung diskutiert.

Technische Universität Braunschweig, Ins Chemie, Hagenring 30, 38106 Braunschweig University of North Carolina at Chapel Hil North Carolina 27599-3290, USA University of Erlangen-Nürnberg, Departm Chemistry, Egerlandstr. 1, 91058 Erlangen, Université de Toulouse, INSA-UPS-LPCNO, C 31077 Toulouse, France. E-mail: laurent.ma † Electronic supplementary information ( additional experimental and structural d susceptibility studies, Fe Mössbauer s CCDC 1531255–1531264. For ESI and c electronic format see DOI: 10.1039/c7sc00 Cite this: Chem. Sci., 2017, 8, 4108

AbstractFerrocene, Cp2Fe, is quantitatively protonated in a mixture of liquid HF/PF5 to yield [Cp2FeH](PF6), which was characterized by 1H/13C NMR and 57Fe Mössbauer spectroscopy as well as single‐crystal X‐ray diffraction analysis. X‐ray diffraction analysis at 100 K revealed a disordered, iron‐coordinated hydrido ligand, which was unambiguously located by aspherical atom refinement at 100 K, and by analyzing the non‐disordered crystal structure at 30 K, revealing a non‐agostic structure.

Facile pseudohalide activation occurs in the reaction of SCN−, SeCN−and N3−with the iron half-sandwich [Cp′Fe(μ-I)]2.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

AbstractEine vollständige Serie von biomimetischen [2Fe‐2S]‐Clustern [(LDepFe)2(μ‐S)2] (3, LDep=CH[CMeN(2,6‐Et2C6H3)]2), [(LDepFe)2(μ‐S)2K] (4), [(LDepFe)2(μ‐S)2][Bu4N] (5, Bu=n‐butyl) und [(LDepFe)2(μ‐S)2K2] (6) wurde hergestellt und charakterisiert. Das homovalente [2Fe(3+/3+)‐2S]‐Cluster 3 ist durch die Reaktion von [(LDepFe)2(μ‐H)2] 2 mit elementarem Schwefel zugänglich. Die chemische Reduktion von 3 mit einem Moläquivalent elementaren Kalium ergibt das Kontaktionenpaar K+[2Fe‐2S]− (4) in Form eines eindimensionalen Koordinationspolymers, das sich wiederum mit [Bu4N]Cl zum separierten Ionenpaar [Bu4N]+[2Fe‐2S]− (5) umsetzen lässt. Weitere Reduktion von 4 mit Kalium erlaubt den Zugang zum superreduzierten homovalenten [2Fe(2+/2+)‐2S]‐Cluster 6. Bemerkenswert hierbei ist, dass es sich bei den Komplexen 4 und 5 um [2Fe‐2S]‐Cluster mit einem jeweils stark delokalisierten Fe2+Fe3+‐Paar handelt, was durch 57Fe‐Mößbauer‐, Röntgenabsorptions‐ und Röntgenemissionsspektroskopie (XAS, XES) in Übereinstimmung mit DFT‐Rechnungen gesichert ist.

We report on an effective cluster expansion of CuBr-linked aggregates by the increase of the steric bulk of the CpR ligand in the pentatopic molecules [CpRFe(η5-P5)]. Using [CpBIGFe(η5-P5)] (CpBIG=C5(4-nBuC6H4)5), the novel multishell aggregate [{CpBIGFe(η5:2:1:1:1:1:1-P5)}12(CuBr)92] is obtained. It shows topological analogy to the theoretically predicted I-C140 fullerene molecule. The spherical cluster was comprehensively characterized by various methods in solution and in the solid state.