A Saddle-Shaped Expanded Porphyrinoid Fitting C.

We present the synthesis of a new type of an expanded porphyrinoid macrocycle with a saddle-shaped morphology and its complexation of C guest molecules. The new macrocycle contains four carbazole and four triazole moieties and can be readily synthesized via a copper-catalyzed click reaction. It shows specific photo-physical properties including fluorescence with a high quantum yield of 60 %.

The Fascinating Flexibility and Coordination Modes of a Pentamethylene Connected Macrocyclic CNC Pincer Ligand.

The coordination chemistry of an electron-rich macrocyclic CNC pincer-ligand consisting of two pentamethylene tethered N-heterocyclic carbene moieties on a carbazole backbone (bimca) is investigated by mainly NMR spectroscopy and X-ray crystal structure analysis. A bridging coordination mode is found for the lithium complex. With the larger and softer potassium ion, the ligand adopts a facial coordination mode and a polymeric structure by intermolecular potassium nitrogen interactions.

Carbenaporphyrins: No Longer Missing Ligands in N-Heterocyclic Carbene Chemistry.

The synthesis of an NHC-containing porphyrinoid ligand is presented. The formally antiaromatic 20 πe macrocyclic framework can be obtained via a 1,3-dipolar cycloaddition ("click-reaction") to form two triazole moieties which were alkylated to the respective triazolium macrocycle. Deprotonation of the ligand precursor with lithium bases to the respective dilithio carbenaporphyrin complex and transmetallation to scandium lead to complexes that exhibit orange fluorescence.

Electron-Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes.

The synthesis of electron-poor mono-, di- and tri(imidazolium)-substituted Cp-ylides is presented and their electronic properties are discussed based on NMR spectroscopy, X-ray structure analyses, electrochemical investigations and DFT calculations as well as by their reactivity toward [Ru(CH CN) Cp*](PF ). With mono- and di(imidazolium)-substituted cyclopentadienides the respective monocationic and dicationic ruthenocences are formed (X-ray), whereas tri(imidazolium) cyclopentadienides are too electron-poor to form the ruthenocenes. Cyclic voltammetric analysis of the ruthenocenes shows reversible oxidation at a potential that increases with every additional electron-withdrawing imidazolium substituent at the Cp ligand by 0.

Deoxygenation of Epoxides with Carbon Monoxide.

The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80-120 °C.

Regio- and chemoselective rearrangement of terminal epoxides into methyl alkyl and aryl ketones.

The development of the highly active pincer-type rhodium catalyst 2 for the nucleophilic Meinwald rearrangement of functionalised terminal epoxides into methyl ketones under mild conditions is presented. An excellent regio- and chemoselectivity is obtained for the first time for aryl oxiranes.

Synthesis of a lithium-cyclopentadienide complex by addition of LiNTf to a zwitterionic fulvalene.

The synthesis of a η-coordinated LiCp complex by simple addition of a Li-salt in benzene is presented. A strongly zwitterionic fulvalene serves as the Cp-precursor. Evidence for the coordination of Li was obtained by the characterisitic Li NMR chemical shifts, variable temperature experiments in solution and by X-ray structure analysis in the solid state.

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes.

Rh(CO)Cl(NHC) complexes of dipyrido-annelated N-heterocyclic carbenes were prepared. From the C-H coupling constant of the respective imidazolium salts and the N-C-N angle of the N-heterocyclic carbene (NHC), a weaker σ-donor character than that of typical unsaturated NHCs is expected. However, the IR stretching frequencies of their Rh(CO)Cl complexes suggest an electron-donor character even stronger than that of saturated NHCs.

Selective rearrangement of terminal epoxides into methylketones catalysed by a nucleophilic rhodium-NHC-pincer complex.

An efficient Rh(I)-NHC-pincer catalyst for the highly regioselective Meinwald rearrangement of monoalkylated epoxides into methylketones under mild conditions is presented. The nucleophilic epoxide opening is assisted by Lewis acids.

Electrosynthesis of imidazolium carboxylates.

Synthesis of imidazolium carboxylate compounds was efficiently achieved by electrochemical reduction of imidazolium precursors under very mild conditions.

Consequences of the one-electron reduction and photoexcitation of unsymmetric bis-imidazolium salts.

Coupling of uronium salts with in situ generated N-heterocyclic carbenes provides straightforward access to symmetrical [4](2+) and unsymmetrical bis-imidazolium salts [6](2+) and [9](2+) . As indicated by cyclic and square-wave voltammetry, [6](2+) and [9](2+) can be (irreversibly) reduced by one electron. The initially formed radicals [6](.

Controlling the coordination modes of a new and highly flexible ligand bearing two N-heterocyclic carbene moieties at a bipyridine backbone.

A new and highly flexible biscarbene ligand with two imidazolin-2-ylidene moieties in 6,6'-position of a 2,2'-bipyridine was prepared and structurally characterised by X-ray analysis. Various silver complexes were prepared from the imidazolium salts. Depending on the counterion, the coordination mode of the ligand can be mono- or bidentate.

X-ray crystal structures of 10pi- and 14pi-electron pyrido-annelated N-heterocyclic carbenes.

The first X-ray crystal structures of mono- and dipyridoimidazolinylidenes are presented, and the size of the carbene N-C-N angles discussed and correlated with the 13C NMR chemical shifts.

Experimental and computational evidence for a boron-assisted, sigma-bond metathesis pathway for alkane borylation.

Photoejection of one CO ligand from isolated CpM(CO)n+1BR2 (n = 1: M = Fe, Ru; n = 2: M = Mo,W; R2 = catecholate or pinacolate) compounds produces a coordinatively unsaturated 16 e- intermediate, a cyclic dioxaboryl transition metal complex, that can efficiently and selectively initiate regioselective C-H bond activation and can be used in the functionalization of alkanes. This chemistry appears distinct from that reported previously for related CpM(CO)n complexes of alkyl and aryl ligands. We show here by a combination of experimental and theoretical studies that the "unoccupied" p orbital of dioxaboryl ligands are intimately involved in the C-H bond activation step and that this hydrogen transfer to boron occurs by a boron-assisted, metal-mediated sigma-bond metathesis.