Manganese and iron PCP pincer complexes - the influence of sterics on structure and reactivity.

The syntheses of various manganese and iron PCP pincer complexes a solvothermal oxidative addition methodology is described. Upon reacting [Mn(CO)] with the ligands (P(C-Br)P-iPr) (1a) and (P(C-Br)P-iPr) (1b), Mn(I) PCP pincer complexes [Mn(PCP-iPr)(CO)] (2a) and [Mn(-PCP-iPr)(CO)] (2b) were obtained. Protonation of 2a with HBF·EtO led to the formation of [Mn(κ,,-P(CH)P-iPr)(CO)]BF (3) featuring an η-C-H agostic bond.

Hydroboration of Terminal Alkenes and trans-1,2-Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex.

A Mn -catalyzed hydroboration of terminal alkenes and a 1,2-diboration of terminal alkynes with pinacolborane (HBPin) is described. For alkenes, anti-Markovnikov hydroboration takes place; for alkynes the reaction proceeds with excellent trans-1,2-selectivity. The most active pre-catalyst is bench-stable alkyl bisphosphine Mn complex fac-[Mn(dippe)(CO) (CH CH CH )].

Structural and Electronic Properties of Iron(0) PNP Pincer Complexes.

In the present work we have prepared and fully characterized several Fe(0) complexes of the type [Fe(PNP)(CO)] treating Fe(II) complexes [Fe(PNP)(Cl)] with KC in the presence of carbon monoxide. While complexes [Fe(PNP-Pr)(CO)], [Fe(PNP-Pr)(CO)] adopt a trigonal bipyramidal geometry, the bulkier and more electron rich [Fe(PNP-Bu)(CO)] is closer to a square pyramidal geometry. Mössbauer spectra showed isomer shifts very close to 0 and similar to those reported for Fe(I) systems.

Synthesis and Catalytic Reactivity of Cobalt Pincer Nitrosyl Hydride Complexes.

The synthesis, characterization, and catalytic activity of low-spin {CoNO} pincer complexes of the type [Co(PCP)(NO)(H)] are described. These compounds are obtained either by reacting [Co(PCP)(κ-BH)] with NO and EtN or, alternatively, by reacting [Co(PCP)(NO)] with boranes, such as NH·BH in solution. The five-coordinate, diamagnetic Co(III) complex [Co(PCP-Pr)(NO)(H)] was found to be the active species in the hydroboration of alkenes with anti-Markovnikov selectivity.

A monochromatic confocal micro-x-ray fluorescence (μXRF) spectrometer for the lab.

Confocal micro-x-ray fluorescence (μXRF) is a powerful tool to analyze the spatial distribution of major, minor, and trace elements in three dimensions. Typical (confocal) μXRF measurements in the lab use polychromatic excitation, complicating quantification and fundamental parameter-based corrections and furthermore deteriorating peak-to-background ratios due to scattered bremsstrahlung. The goal for the new setup was to remedy these problems, without sacrificing spatial resolution, and keep it flexible for different excitation energies and transportation to other sources.

CuSO/[Cu(NH)]SO-Composite Thermochemical Energy Storage Materials.

The thermochemical energy-storage material couple CuSO/[Cu(NH)]SO combines full reversibility, application in a medium temperature interval (<350 °C), and fast liberation of stored heat. During reaction with ammonia, a large change in the sulfate solid-state structure occurs, resulting in a 2.6-fold expansion of the bulk material due to NH uptake.

Synthesis, Characterization, and Catalytic Reactivity of {CoNO} PCP Pincer Complexes.

The reaction of coordinatively unsaturated Co(II) PCP pincer complexes with nitric oxide leads to the formation of new, air-stable, diamagnetic mono nitrosyl compounds. The synthesis and characterization of five- and four-coordinate Co(III) and Co(I) nitrosyl pincer complexes based on three different ligand scaffolds is described. Passing NO through a solution of [Co(PCP-Pr)Cl], [Co(PCP-Pr)Cl] or [Co(PCP-Pr)Br] led to the formation of the low-spin complex [Co(PCP-Pr)(NO)X] with a strongly bent NO ligand.

Structures and Chemical Bonding in Antimony(III) Bromide Complexes with Pyridine.

Weakly or "partially" bonded molecules are an important link between the chemical and van der Waals interactions. Molecular structures of six new SbBr -Py complexes in the solid state have been determined by single-crystal X-ray diffraction analysis. In all complexes all Sb atoms adopt a pseudo-octahedral coordination geometry which is completed by additional Sb⋅⋅⋅Br contacts shorter than the sum of the van der Waals radii, with Br-Sb⋅⋅⋅Br angles close to 180°.

Ammonium bis(salicylaldehyde thiosemicarbazonato)ferrate(III), a supramolecular material containing low-spin Fe.

The synthesis and crystal structure (100 K) of the title compound, ammonium bis[salicylaldehyde thiosemicarbazonato(2-)-κO,N,S]iron(III), NH[Fe(CHNOS)], is reported. The asymmetric unit consists of an octahedral [Fe(thsa)] fragment, where thsa is salicylaldehyde thiosemicarbazonate(2-), and an NH cation. Each thsa ligand binds via the thiolate S, the imine N and the phenolate O donor atoms, resulting in an FeSNO chromophore.

Double Ring-Closing Approach for the Synthesis of 2,3,6,7-Substituted Anthracene Derivatives.

A method for the synthesis of 2,3,6,7-substituted anthracene derivatives, one of the most challenging anthracene substitution patterns to obtain, is presented. The method is exemplified by the preparation of 2,3,6,7-anthracenetetracarbonitrile and employs a newly developed, stable, protected 1,2,4,5-benzenetetracarbaldehyde as the precursor. The precursor can be obtained in two scalable synthetic steps from 2,5-dibromoterephthalaldehyde and is converted into the anthracene derivative by a double intermolecular Wittig reaction under very mild conditions, followed by a deprotection and intramolecular double ring-closing condensation reaction.

Access to Fe Bis(σ-B-H) Aminoborane Complexes through Protonation of a Borohydride Complex and Dehydrogenation of Amine-Boranes.

Herein, we report on the first synthesis and structural characterization of the iron based aminoborane complexes [Fe(PNP)(H)(η :η -H B=NR )] (R=H, Me). These species are formed upon protonation of the borohydride complex [Fe(PNP)(H)(η -BH )] by ammonium salts [NH R ] (R=H, Me). For R=Me, the reaction proceeds via the cationic dinuclear intermediate [{Fe(PNP)(H)} (μ ,η :η -BH )] .

Five-Coordinate Low-Spin {FeNO} PNP Pincer Complexes.

The synthesis and characterization of air-stable cationic mono nitrosonium Fe(I) PNP pincer complexes of the type [Fe(PNP)(NO)Cl] are described. These complexes are obtained via direct nitroslyation of [Fe(PNP)Cl] with nitric oxide at ambient pressure. On the basis of magnetic and EPR measurements as well as DFT calculations, these compounds were found to adopt a low-spin d configuration and feature a nearly linear bound NO ligand suggesting FeNO rather than FeNO character.

Azaindolo[3,2,1-jk]carbazoles: New Building Blocks for Functional Organic Materials.

The preparation and characterization of 12 azaindolo[3,2,1-jk]carbazoles is presented. Ring-closing C-H activation allowed for the convenient preparation of six singly and six doubly nitrogen-substituted indolo[3,2,1-jk]carbazole derivatives in which ten of the materials have not been described in the literature before. The detailed photophysical and electrochemical characterization of the developed materials revealed a significant impact of the incorporation of pyridine-like nitrogen into the fully planar indolo[3,2,1-jk]carbazole backbone.

Selective Hydrogenation of Aldehydes Using a Well-Defined Fe(II) PNP Pincer Complex in Biphasic Medium.

A biphasic process for the hydrogenation of aldehydes was developed using a well-defined iron (II) PNP pincer complex as model system to investigate the performance of various ionic liquids. A number of suitable hydrophobic ionic liquids based on the N(Tf) anion were identified, allowing to immobilize the iron (II) catalyst in the ionic liquid layer and to facilitate the separation of the desired alcohols. Further studies showed that targeted Brønsted basic ionic liquids can eliminate the need of an external base to activate the catalyst.

Hydrogenation of Nitriles and Ketones Catalyzed by an Air-Stable Bisphosphine Mn(I) Complex.

Efficient hydrogenations of nitriles and ketones with molecular hydrogen catalyzed by a well-defined bench-stable bisphosphine Mn(I) complex are described. These reactions are environmentally benign and atomically economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. A range of aromatic and aliphatic nitriles and ketones were efficiently converted into primary amines and alcohols, respectively, in good to excellent yields.

Cycle Stability and Hydration Behavior of Magnesium Oxide and Its Dependence on the Precursor-Related Particle Morphology.

Thermochemical energy storage is considered as an auspicious method for the recycling of medium-temperature waste heat. The reaction couple Mg(OH)₂⁻MgO is intensely investigated for this purpose, suffering so far from limited cycle stability. To overcome this issue, Mg(OH)₂, MgCO₃, and MgC₂O₄·2H₂O were compared as precursor materials for MgO production.

Iron PCP Pincer Complexes in Three Oxidation States: Reversible Ligand Protonation To Afford an Fe(0) Complex with an Agostic C-H Arene Bond.

In the current investigation, the reaction of Fe(CO) with the ligand precursor 2-chloro-N,N-bis(diisopropylphosphanyl)-N,N-diethylbenzene-1,3-diamine (P(C-Cl)P- iPr) (1) was investigated. When a suspension of Fe(CO) and 1 in CHCN was transferred in a sealed microwave glass vial and stirred for 18 h at 110 °C the complex [Fe(PCP- iPr)(CO)Cl] (2) was obtained. In an attempt to prepare the hydride Fe(II) complex [Fe(PCP- iPr)(CO)H] (3), 2 was reacted with 1 equiv of Li[HBEt] in THF.

Chemoselective Hydrogenation of Aldehydes under Mild, Base-Free Conditions: Manganese Outperforms Rhenium.

Several hydride Mn(I) and Re(I) PNP pincer complexes were applied as catalysts for the homogeneous chemoselective hydrogenation of aldehydes. Among these, [Mn(PNP-Pr)(CO)(H)] was found to be one of the most efficient base metal catalysts for this process and represents a rare example which permits the selective hydrogenation of aldehydes in the presence of ketones and other reducible functionalities, such as C=C double bonds, esters, or nitriles. The reaction proceeds at room temperature under base-free conditions with catalyst loadings between 0.

Formation of Mono Oxo Molybdenum(IV) PNP Pincer Complexes: Interplay between Water and Molecular Oxygen.

The synthesis of cationic mono oxo Mo PNP pincer complexes of the type [Mo(PNP-Pr)(O)X] (X = I, Br) from [Mo(PNP-Pr)(CO)X] is described. These compounds are coordinatively unsaturated and feature a strong Mo≡O triple bond. The formation of these complexes proceeds via cationic 14e intermediates [Mo(PNP-Pr)(CO)X] and requires both molecular oxygen and water.

Charge-transfer states in triazole linked donor-acceptor materials: strong effects of chemical modification and solvation.

A series of 1,2,3-triazole linked donor-acceptor chromophores are prepared by Click Chemistry from ene-yne starting materials. The effects of three distinct chemical variations are investigated: enhancing the acceptor strength through oxidation of the sulphur atom, alteration of the double bond configuration, and variation of the triazole substitution pattern. A detailed photophysical characterization shows that these alterations have a negligible effect on the absorption while dramatically altering the emission wavelengths.