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The position of the hydrogen atom inside the strong and short intramolecular hydrogen bond of the hydrogen maleate anion strongly varies depending on the crystalline environment. Therefore, it has not been possible in the past to accurately determine it using X-ray diffraction data although there are 292 hydrogen maleate crystal structures with different cations in the literature. In this study, a geometric correlation for the accurate prediction of the hydrogen position in the short intramolecular hydrogen bond is presented. The results used to derive the correlation are obtained from low-temperature neutron-diffraction studies on nine different hydrogen maleate salts that span the whole range from perfectly symmetric to highly asymmetric intramolecular hydrogen bonds. Since the only variable in the correlation as derived from the neutron data is the O...O distance, the hydrogen atom position in question can subsequently be predicted using information that is accurately available from routine X-ray data. The procedure is tested using high-resolution low-temperature synchrotron X-ray diffraction structures of the same compounds, before it is applied to X-ray data sets found in the literature in which the hydrogen atom position was not determined accurately or not determined at all, e.g., using a riding model. [ABSTRACT FROM AUTHOR]

A PP(O)P pincer ligand based upon a peri -substituted acenaphthyl (Ace) scaffold and a secondary phosphine oxide, (5-Ph 2 P-Ace-6-) 2 P(O)H, was prepared and fully characterized including a neutron diffraction study. The reaction with [Ni(H 2 O) 6 ]Cl 2 and PdCl 2 produced ionic metal(II) complexes [κ 3 - P , P' , P'' ((5-Ph 2 P-Ace-6-) 2 P(OH))MCl]Cl, which upon addition of Et 3 N gave rise to zwitterionic metal(II) complexes κ 3 - P , P' , P'' ((5-Ph 2 P-Ace-6-) 2 P(O))MCl (M = Ni, Pd). The reaction with Ni(COD) 2 (COD = cyclooctadiene) provided the η 3 -cyclooctenyl Ni(II) complex κ 3 - P , P' , P'' ((5-Ph 2 P-Ace-6-) 2 P(O))Ni(η 3 -C 8 H 13 ). A detailed complementary bonding analysis of the P-H, P-O, and P-M interactions was carried out (M = Ni, Pd).

The synthesis, characterization, biological activity, and toxicology of sila-ibuprofen, a silicon derivative of the most common nonsteroidal anti-inflammatory drug, is reported. The key improvements compared with ibuprofen are a four times higher solubility in physiological media and a lower melting enthalpy, which are attributed to the carbon-silicon switch. The improved solubility is of interest for postsurgical intravenous administration. A potential for pain relief is rationalized via inhibition experiments of cyclooxygenases I and II (COX-I and COX-II) as well as via a set of newly developed methods that combine molecular dynamics, quantum chemistry, and quantum crystallography. The binding affinity of sila-ibuprofen to COX-I and COX-II is quantified in terms of London dispersion and electrostatic interactions in the active receptor site. This study not only shows the potential of sila-ibuprofen for medicinal application but also improves our understanding of the mechanism of action of the inhibition process.

A proximity enforcing diarylsilane ligand is reported, which gives rise to unusual Si-H···M interactions with the d 10 metal ions Cu + and Ag + upon complexation. These interactions are studied in detail both experimentally and computationally and can be classified to be weakly agostic in nature for the Si-H···Cu interaction. The Si-H···Ag interaction has more signatures of an electrostatic contact.

In the family of metallocenes, MgCp* 2 (Cp* = pentamethylcyclopentadienyl) exhibits a regular linear sandwich structure, whereas CaCp* 2 is bent in both the gas phase and solid state. Bending is typically observed for metal ions which possess a lone pair. Here, we investigate which electronic differences cause the bending in complexes lacking lone pairs at the metal atoms. The bent gas-phase geometry of CaCp* 2 suggests that the bending must have an intramolecular origin. Geometry optimizations with and without dispersion effects/d-type polarization functions on MCp 2 and MCp* 2 gas-phase complexes (M = Ca, Mg) establish that attractive methyl···methyl London dispersion interactions play a decisive role in the bending in CaCp* 2 . A sufficient polarizability of the metal to produce a shallow bending potential energy curve is a prerequisite but is not the reason for the bending. Concomitant ligand-induced charge concentrations and localizations at the metal atoms are studied in further detail, for which real-space bonding and orbital-based descriptors are used. Low-temperature crystal structures of MgCp* 2 and CaCp* 2 were determined which facilitated the identification and characterization of intermolecular pseudo-pregostic interactions, C-H···Ca, in the CaCp* 2 crystal structure.