A series of unprecedented organoiron complexes of the formal oxidation states −2, 0, +1, +2, and +3 is presented, which are largely devoid of stabilizing ligands and, in part, also electronically unsaturated (14-, 16-, 17- and 18-electron counts). Specifically, it is shown that nucleophiles unable to undergo β-hydride elimination, such as MeLi, PhLi, or PhMgBr, rapidly reduce Fe(3+) to Fe(2+) and then exhaustively alkylate the metal center. The resulting homoleptic organoferrate complexes [(Me4Fe)(MeLi)][Li(OEt2)]2 (3) and [Ph4Fe][Li(Et2O)2][Li(1,4-dioxane)] (5) could be characterized by X-ray crystal structure analysis. However, these exceptionally sensitive compounds turned out to be only moderately nucleophilic, transferring their organic ligands to activated electrophiles only, while being unable to alkylate (hetero)aryl halides unless they are very electron deficient. In striking contrast, Grignard reagents bearing alkyl residues amenable to β-hydride elimination reduce FeXn (n = 2, 3) to clusters of...

Preparation, Structure, and Reactivity of Nonstabilized Organoiron Compounds. Implications for Iron-Catalyzed Cross Coupling Reactions

https://kops.uni-konstanz.de/bitstream/handle/123456789/10014/2000_CoordChemRev_203_325_Mecking.pdf;sequence=1

Cationic nickel and palladium complexes with bidentate ligands for the CC linkage of olefins

The combination of a magnesium anode with a sulfur cathode is one of the most promising electrochemical couples because of its advantages of good safety, low cost, and a high theoretical energy density. However, magnesium sulfur batteries are still in a very early stage of research and development, and the discovery of suitable electrolytes is the key challenge for further improvement. Here, a new preparation method for non-nucleophilic electrolyte solutions using a two-step reaction in one-pot is presented, which provides a feasible way to optimize the physiochemical properties of the electrolyte for the application in magnesium sulfur batteries. The first use of modified electrolytes in glymes and binary solvents of glyme and ionic liquid shows beneficial effects on the performance of magnesium sulfur batteries. New insights into the reaction mechanism of electrochemical conversion between magnesium and sulfur are also investigated.

Performance Improvement of Magnesium Sulfur Batteries with Modified Non‐Nucleophilic Electrolytes

Publisher Summary This chapter surveys the rapidly growing field comprising the chemistry of transition metal complexes containing ligands which are made up only of carbon atoms within their coordination spheres. The chapter describes metal complexes which contain linear or cyclic ligands of composition C n (n n ligands, in order of increasing carbon content of the ligand have been discussed. This is followed by a discussion on complexes of cyclic all-carbon ligands, such as [C 3 {Fe(CO) 2 Cp} 3 ] + . Complexes containing C n ligands associated with binuclear metal–metal bonded systems are followed by an account of metal cluster complexes containing C n ligands. It also includes hybrid complexes where a cluster supports a C n ligand also attached to a mononuclear metal–ligand fragment. The study is broadly based on a group-by-group approach and includes salient details of synthesis, properties, chemistry and electronic structure.

Transition Metal Complexes Containing All-Carbon Ligands

Open-Shell Organometallics as a Bridge between Werner-Type and Low-Valent Organometallic Complexes. The Effect of the Spin State on the Stability, Reactivity, and Structure.

Es wird uber ESR-Untersuchungen am homoleptischen σ-Arylubergangsmetallkation Tetramesitylmolybdan(V) berichtet. Die ESR-Parameter konnen mit einem D2d-Ligandenfeld-Modell (verzerrtes Tetraeder, B1-Grundzustand) interpretiert werden. Durch Analyse der 95,97Mo-Hyperfeinstruktur werden die Hyperfeinstrukturparameter P und K abgeleitet. Sie zeigen eine sehr niedrige effektive Kernladung am Molybdan – ≈ + 0,4 – und eine im Vergleich zum Tetramesitylvanadium(IV) merklich hohere Kovalenz der MoC-σ-Bindungen an. Der nur schwach anisotrope g-Tensor weist auf das Vorhandensein starker „charge-transfer”-Wechselwirkungen hin.



ESR Investigations on Tetramesityl Molybdenum(V) – a Homoleptic σ-Aryl Transition Metal Cation



An ESR investigation on the homoleptic σ-aryl transition metal cation tetramesityl molybdenum(V) is reported. The ESR parameters can be interpreted by means of a D2d ligandfield model (distorted tetrahedral symmetry, B1 ground state). Analyzing the 95,97Mo hyperfine splitting the hyperfine parameters P and K are derived. They indicate a very low value for the effective nuclear charge on the molybdenum: ≈ +0.4. The covalency degree of the MoC σ bonds is considerably larger than that observed for tetramesityl vanadium(IV). The small anisotropy of the g tensor indicates the presence of remarkable charge-transfer interactions.

ESR-Untersuchungen an Tetramesitylmolybdän(V) – einem homoleptischen σ-Arylübergangsmetallkation

Die Synthesen der Verbindungen MesMe2SiCl, MesMe2SiBr, MesMe2SiC5H5, MesMe2SiC2Ph, MesMe2SiPh, MesMe2SiNEt2, MesMe2SiN2C3H3, MesMe2SiNC8H6, (MesMe2Si)2NH, (MesMe2Si)2 und die Herstellung von Losungen der Silyllithium- und Silylkaliumverbindung werden beschrieben. Die Verbindungen werden durch 1H-NMR-Spektroskopie, 13C-NMR-Spektroskopie und Elementaranalyse charakterisiert.



Synthesis and Characterization of Reagents with the Mesityldimethylsilyl Group



The syntheses of MesMe2SiCl, MesMe2SiBr, MesMe2SiC5H5, MesMe2SiC2Ph, MesMe2SiPh, MesMe2SiNEt2, MesMe2SiN2C3H3, MesMe2SiNC8H6, (MesMe2Si)2NH, (MesMe2Si)2, and the preparation of solutions of the silyllithium and silylpotassium compound are reported. The compounds are characterized by 1H NMR spectroscopy, 13C NMR spectroscopy, and elemental analysis.

Darstellung und Charakterisierung von Reagenzien mit der Mesityldimethylsilylgruppe

Es wird uber Komplexverbindungen des Dipiperidino-diphenyl-biphsophins mit Salzen der ersten und zweiten Nebengruppe berichtet. Sie zeigen eine geringere Stabilitat als die Komplexe des Dipiperidino-dicyclohexyl-biphosphins, die sich in einer verstarkten Tendenz zur Disproportionierung in Monophosphinkomplexe unter Abspaltung von Cyclopolyphosphinen ausert. Mit Quecksilberjodid wurde keine definierte Substanz erhalten.



Complex compounds of dipiperidino-diphenyl-biphosphine with metal salts of the first and second subgroup are described. Compared with dipiperidino-dicyclohexyl-biphosphine complexes, a lower stability is observed indicated by the stronger tendency of dismutation into monophosphine complexes and cyclopolyphosphines. No definite HgJ2 complexes have been obtained.

Komplexbildung mit Amino‐Phosphinen. II. Komplexverbindungen des Dipiperidino‐diphenyl‐biphosphins und des Dipiperidino‐phenyl‐phosphins mit d10‐Metallionen

W. Seidel

Papers

ESR-Untersuchungen an Tetramesitylmolybdän(V) – einem homoleptischen σ-Arylübergangsmetallkation

Darstellung und Charakterisierung von Reagenzien mit der Mesityldimethylsilylgruppe

Komplexbildung mit Amino‐Phosphinen. II. Komplexverbindungen des Dipiperidino‐diphenyl‐biphosphins und des Dipiperidino‐phenyl‐phosphins mit d10‐Metallionen

σ‐Organokomplexe des Vanadyl(IV)‐Ions

Zur Synthese vom Oxovanadiumtrimesityl