H/D exchange under mild conditions in arenes and unactivated alkanes with C6D6 and D2O using rigid, electron-rich iridium PCP pincer complexes

The synthesis and characterization of an iridium polyhydride complex (Ir-H4) supported by an electron-rich PCP framework is described. This complex readily loses molecular hydrogen allowing for rapid room temperature hydrogen isotope exchange (HIE) at the hydridic positions and the α-C-H site of the ligand with deuterated solvents such as benzene-d6, toluene-d8 and THF-d8. The removal of 1-2 equivalents of molecular H2 forms unsaturated iridium carbene trihydride (Ir-H3) or monohydride (Ir-H) compounds that are able to create further unsaturation by reversibly transferring a hydride to the ligand carbene carbon. These species are highly active hydrogen isotope exchange (HIE) catalysts using C6D6 or D2O as deuterium sources for the deuteration of a variety of substrates. By modifying conditions to influence the Ir-Hn speciation, deuteration levels can range from near exhaustive to selective only for sterically accessible sites. Preparative level deuterations of select substrates were performed allowing for procurement of >95% deuterated compounds in excellent isolated yields; the catalyst can be regenerated by treatment of residues with H2 and is still active for further reactions.

The Unexpected Role of SeVI Species in Epoxidations with Benzeneseleninic Acid and Hydrogen Peroxide

Benzeneperoxyseleninic acid has been proposed as the key intermediate in the widely used epoxidation of alkenes with benzeneseleninic acid and hydrogen peroxide. However, it reacts sluggishly with cyclooctene and instead rapidly decomposes in solution to a mixed selenonium-selenonate salt that was identified by X-ray absorption and 77 Se NMR spectroscopy, as well as by single crystal X-ray diffraction. This process includes a selenoxide elimination of the peroxyseleninic acid with liberation of oxygen and additional redox steps. The salt is relatively stable in the solid state, but generates the corresponding selenonic acid in the presence of hydrogen peroxide. The selenonic acid is inert towards cyclooctene on its own; however, rapid epoxidation occurs when hydrogen peroxide is added. This shows that the selenonic acid must first be activated through further oxidation, presumably to the heretofore unknown benzeneperoxyselenonic acid. The latter is the principal oxidant in this epoxidation.

Particle size dependence of proton conduction in a cationic lanthanum phosphonate MOF

Particle size-dependent proton conduction is studied in a lanthanum(iii) metal–organic framework, PCMOF21-AcO [La₂(H2L)_1.5(AcO)₃·(H₂O)_5.59], with a 3-D network linked by dicationic bis(dimethylphosphonato)bipiperidinium units.

Tandem deoxygenative hydrosilation of carbon dioxide with a cationic scandium hydridoborate and B(C6F5)3

A scandium hydridoborate complex supported by the dianionic pentadentate ligand B₂Pz₄Py is prepared via hydride abstraction from the previously reported scandium hydride complex with tris-pentafluorophenyl borane.

Boron-nitrogen substituted dihydroindeno[1,2-b]fluorene derivatives as acceptors in organic solar cells

The electrophilic borylation of 2,5-diarylpyrazines results in the formation of boron-nitrogen doped dihydroindeno[1,2-b]fluorene which can be synthesized using standard Schlenk techniques and worked up and handled readily under atmospheric conditions. Through transmetallation via diarylzinc reagents a series of derivatives were synthesized which show broad visible to near-IR light absorption profiles that highlight the versatility of this BN substituted core for use in optoelectronic devices. The synthesis is efficient, scalable and allows for tuning through changes in substituents on the planar heterocyclic core and at boron. Exploratory evaluation in organic solar cell devices as non-fullerene acceptors gave power conversion efficiencies of 2%.

3D porous metal-organic framework for selective adsorption of methane over dinitrogen under ambient pressure

We report a highly porous 3D metal-organic framework (MOF) that shows potential for coal mine methane (CMM) capture.

Methionine Binding to Dirhodium(II) Tetraacetate

The reaction between antitumor active dirhodium(II) tetraacetate and dl-methionine (HMet) was followed in aqueous solution and showed initially mixtures of 1:1 and 1:2 adducts [Rh2(AcO)4(HMet)(H2O)] (AcO- = CH3COO-) and [Rh2(AcO)4(HMet)2] formed at room temperature (RT), as evidenced by UV-vis spectroscopy and electrospray ionization mass spectrometry (ESI-MS). Rh K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy confirmed methionine thioether binding to the axial positions of the Rh2(AcO)4 cage structure. With excess HMet at RT, stepwise displacement of the acetate groups was observed after some time using ESI-MS. Heating the solution to 40° for 24 h accelerated the substitution reaction leading to stable dirhodium(II) species with two acetate ligands displaced by two methionine groups. The crystal structure of the purple [RhII2(AcO)2(d-Met)(l-Met)]·6H2O compound obtained from the solution revealed tridentate coordination of the methionine ligands to the Rh(II) ions, with the thioether S atoms in equatorial positions. A minor amount of a light orange monomeric [RhIII(Met)2](AcO) complex also formed in the solution was isolated by size exclusion chromatography and identified by ESI-MS. Crystals of [RhIII(d-Met)(l-Met)]Cl·3H2O were prepared by reacting RhCl3 and dl-HMet. The crystal structure showed tridentate binding of the methionine ligands to the Rh(III) ion in a trans-S, N, O arrangement.

Microsphere Assemblies via Phosphonate Monoester Coordination Chemistry

By complexing a bent phosphonate monoester ligand with cobalt(II), coupled with in situ ester hydrolysis, coordination microspheres (CALS=CALgary Sphere) are formed whereas the use of the phosphonic acid directly resulted in a sheet-like structure. Manipulation of the synthetic conditions gave spheres with different sizes, mechanical stabilities, and porosities. Time-dependent studies determined that the sphere formation likely occurred through the formation of a Co²⁺ and ligand chain that propagates in three dimensions through different sets of interactions. The relative rates of these assembly processes versus annealing by ester hydrolysis and metal dehydration determine the growth of the microspheres. Hardness testing by nanoindentation is carried out on the spheres and sheets. Notably, no templates or capping agents are employed, the growth of the spheres is intrinsic to the ligand geometry and the coordination chemistry of cobalt(II) and the phosphonate monoester.

Scandium alkyl and hydride complexes supported by a pentadentate diborate ligand: reactions with CO2 and N2O

Alkyl and hydrido scandium complexes of the dianionic pentadentate ligand B2Pz4Py are reported.

Extracting structural trends from systematic variation of phosphonate/phosphonate monoester coordination polymers

Systematic variation of ligand geometry and ester size shows that dimensionality of barium phosphonate/phosphonate ester structures can be truncated by either route.

Dithienophosphole-Based Phosphinamides with Intriguing Self-Assembly Behavior

A new, highly adaptable type of phosphinamide‐based hydrogen bonding is representatively demonstrated in π‐conjugated phosphole materials. The rotational flexibility of these intermolecular P=O−H−N hydrogen bonds is demonstrated by X‐ray crystallography and variable‐concentration NMR spectroscopy. In addition to crystalline compounds, phosphinamide hydrogen bonding was successfully introduced into the self‐assembly of soft crystals, liquid crystals, and organogels, thus highlighting the high general value of this type of interaction for the formation of organic soft materials.

Parameterizing and grading hydrolytic stability in metal–organic frameworks

Water stability of MOFs is reviewed including exposure techniques, characterization methods, and ultimately more consistent definitions of water stability.

Design of a humidity-stable metal-organic framework using a phosphonate monoester ligand

Phosphonate monoesters are atypical linkers for metal-organic frameworks, but they offer potentially added versatility. In this work, a bulky isopropyl ester is used to direct the topology of a copper(II) network from a dense to an open framework, CALF-30. CALF-30 shows no adsorption of N2 or CH4 however, using CO2 sorption, CALF-30 was found to have a Langmuir surface area of over 300 m(2)/g and to be stable to conditions of 90% relative humidity at 353 K owing to kinetic shielding of the framework by the phosphonate ester.