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.

Ligand Influence on Structural and Spectroscopic Properties of Beryllium Oxocarboxylates

Aluminum-based adjuvants for vaccines and beryllium ions interact with the same immune receptor. The Be₄O core, which is also found in beryllium oxocarboxylates, has been proposed to be the binding species in the latter case. However, this is not proven due to a lack of suitable probes for the Be₄O moiety. Therefore, a versatile synthetic route to beryllium oxocarboxylates has been developed to investigate the steric and electronic influence of the ligands onto their molecular and spectroscopic properties. The oxocarboxylates exhibit extremely narrow line widths in ⁹Be NMR spectroscopy, and the chemical shift is only influenced by the sterics of the ligands. The mean variation of the atomic distances in the central Be₄O building block is extremely small over all investigated compounds, and even the C-C distances are only little perturbed by the properties of the ligands. Vibrational spectroscopy showed Be-O bands; however, further distinctions could not be drawn.

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.

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.