The quest for beryllium peroxides

A Personal Account on Inorganic Reaction Mechanisms

The presented Review is focused on the latest research in the field of inorganic chemistry performed by the van Eldik group and his collaborators. The first part of the manuscript concentrates on the interaction of nitric oxide and its derivatives with biologically important compounds. We summarized mechanistic information on the interaction between model porphyrin systems (microperoxidase) and NO as well as the recent studies on the formation of nitrosylcobalamin (CblNO). The following sections cover the characterization of the Ru(II)/Ru(III) mixed-valence ion-pair complexes, including Ru(II)/Ru(III)(edta) complexes. The last part concerns the latest mechanistic information on the DFT techniques applications. Each section presents the most important results with the mechanistic interpretations.

Glutamyl-glutamate – a tailor-made chelating ligand for the [Be4O]6+ core in basic beryllium complexes and implications on investigations on the origins of chronic beryllium disease

Density functional theory calculations suggest that l-glutamyl-l-glutamate [H-Glu-Glu-H]2– can act as an efficient chelating ligand in basic beryllium carboxylates of type Be4O(RCO2)6. An exergonic energy balance of –10.6 kcal mol–1 for the substitution of two [AcO]– anions by one [H-Glu-Glu-OH]2– dianion in Be4O(AcO2)6 has been calculated; for a second and third substitutions, the computed energy release amounts to –9.3, and –11.3 kcal mol–1. The coordination geometry of the complexes shows a trend toward less deviation from local octahedral symmetry with increasing number of [H-Glu-Glu-OH]2– ligands. The implications of these findings for the yet unknown molecular origins of chronic beryllium disease (CBD) are discussed, and a Be4O moiety is suggested as the beryllium species engaged in CBD.

Stable magnesium peroxide at high pressure

Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth’s lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO₂. Raman spectroscopy detects the presence of a peroxide ion (O₂²⁻) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO₂ may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.

Bis(μ-diisopropyl-hydoxylaminato)-κ(2) O:N;κ(2) O:O-bis-[(diisopropyl-hydoxylaminato-κO)beryllium]

The title compound, [Be₂(C₆H₁₄NO)₄], was prepared from a solution of BeCl₂ in diethyl ether and two equivalents of O-lithia­ted N,N-diisopropyl­hydoxyl­amine. The mol­ecular structure is composed of a dinuclear unit forming a central five-membered planar Be—O—Be—O—N ring (sum of inter­nal angles = 540.0°; r.m.s. deviation from planarity = 0.0087 Å). Both Be atoms show the unusual coordination number of three, with one Be atom coordinated by three O atoms and the other by two O atoms and one N atom, both in distorted trigonal–planar environments. The Be—O distances are in the range 1.493 (5)–1.600 (5) Å and the Be—N distance is 1.741 (5) Å.