The Formation of High‐Order Polybromides in a Room‐Temperature Ionic Liquid: From Monoanions ([Br5]− to [Br11]−) to the Isolation of [PC16H36]2[Br24] as Determined by van der Waals Bonding Radii

An unprecedented diversity of high‐order bromine catenates (anionic polybromides) was generated in a tetraalkylphosphonium‐based room temperature ionic liquid system. Raman spectroscopy was used to identify polybromide monoanions ranging from [Br₅]^? to [Br₁₁]^? in the bulk solution, while single‐crystal X‐ray diffraction identified extended networks of linked [Br₁₁]^? units, forming a previously unknown polymeric [Br₂₄]^2? dianion. This represents the largest polybromide species identified to date. In combination with recent work, this suggests that other, higher order molecular polybromide ions might be isolated.     

Hydrogen from Formic Acid through Its Selective Disproportionation over Sodium Germanate—A Non‐Transition‐Metal Catalysis System

A robust catalyst for the selective dehydrogenation of formic acid to liberate hydrogen gas has been designed computationally, and also successfully demonstrated experimentally. This is the first such catalyst not based on transition metals, and it exhibits very encouraging performance. It represents an important step towards the use of renewable formic acid as a hydrogen‐storage and transport vector in fuel and energy applications.     

Molecular Cobalt Clusters as Precursors of Distinct Active Species in Electrochemical,Photochemical, and Photoelectrochemical Water Oxidation Reactions in Phosphate Electrolytes

Three cobalt model molecular compounds, Co‐cubane ([Co₄(µ₃‐O)₄(µ‐OAc)₄py₄]), Co‐trimer ([Co₃(μ₃‐O)(µ‐OAc)₆py₃]PF₆), and Co‐dimer ([Co₂(μ‐OH)₂(µ‐OAc)(OAc)₂py₄]PF₆), are investigated as water oxidation reaction (WOR) catalysts, using electrochemical, photochemical, and photoelectrochemical methodologies in phosphate electrolyte. The actual species contributing to the catalytic activity observed in the WOR are derived from the transformation of these cobalt compounds. The catalytic activity observed is highly dependent on the initial compound structure and on the particular WOR methodology used. Co‐cubane shows no activity in the electrochemical WOR and negligible activity in the photochemical WOR, but is active in the photoelectrochemical WOR, in which it behaves as a precursor to catalytically active species. Co‐dimer also shows no activity in the electrochemical WOR, but behaves as a precursor to catalytically active species in both the photochemical and photoelectrochemical WOR experiments. Co‐trimer behaves as a precursor to catalytically active species in all three of the WOR methodologies.     

Beyond the Halogen Bond: Examining the Limits of Extended Polybromide Networks through Quantum‐Chemical Investigations

The bonding environments of some polybromide monoanions and networks were examined by quantum‐chemical methods to investigate electronic interactions between dibromine–dibromine contacts. Examination of thermodynamic parameters and a bond critical point analysis give strong evidence for such bonding modes, which have been previously treated disparately in the literature. The thermodynamic stability of large polybromides up to [Br₃₇]^? was also predicted by these methods.     

The Role of the Reactor Wall in Hydrothermal Biomass Conversions

The processing of renewable feedstocks to platform chemicals and, to a lesser degree, fuels is a key part of sustainable development. In particular, the combination of lignocellulosic biomass with hydrothermal upgrading (HTU), using high temperature and pressure water (HTPW), is experiencing a renaissance. One of the many steps in this complicated process is the in‐situ hydrogenation of intermediate compounds. As formic acid and related low‐molecular‐weight oxygenates are among the species generated, it is conceivable that they act as a hydrogen source. Such hydrogenations have been suggested to be catalyzed by water, by bases like NaOH, and/or to involve “reactive/nascent hydrogen”. To achieve the temperatures and pressures required for HTU, it is necessary to conduct the reactions in high‐pressure vessels. Metals are typical components of their walls and/or internal fittings. Here, using cyclohexanone as a model compound for more complex biomass‐derived molecules, iron in the wall of high‐pressure stainless steel reactors is shown to be responsible for the hydrogenation of ketones with low‐molecular‐weight oxygenates acting as a hydrogen source in combination with water.     

Ligand-exchange chromatography of amino sugars and amino acids on copper-loaded silylated controlled-pore glass

The application of silylated controlled-pore glass (CPG) particles as a stationary phase for the liquid chromatographic separation of selected amino acids and amino hexoses is reported. Copper-loaded columns prepared from CPG particles whose surface was silylated to immobilize an ethylenediamine functional group were employed. Copper bleeding from the column occurred but was compensated by 10^-4M copper in the ammoniacal eluent. Hydrolysis of the siloxane bonded to the surface limited the practical lifetime of a column to 50 h of continuous operation.