Hydride and halide abstraction reactions behind the enhanced basicity of Be and Mg clusters with nitrogen bases.

In this study, we investigate the protonation effects on the structure, relative stability and basicity of complexes formed by the interaction of monomers and dimers of BeX and MgX (X = H, F) with NH, CHNH, HCN, and NCH bases. Calculations were performed using the M06-2X/aug-cc-pVTZ formalism, along with QTAIM, ELF and NCI methods for electron density analysis and MBIE and LMO-EDA energy decomposition analyses for interaction enthalpies. The protonation of the MH- and MH-Base complexes occurs at the negatively charged hydrogen atoms of the MH and MH moieties through typical hydride abstraction reactions, while protonation at the N atom of the base is systematically less exothermic.

Beryllium as a Base: Complexes of Be(CO) with HX (X=F, Cl, Br, CN, NC, CCH, OH).

Beryllium chemistry is typically governed by its electron deficient character, but in some compounds it can act as a base. In order to understand better the unusual basicity of Be, we have systematically explored the complexes of one such compound, Be(CO), towards several hydrogen bond donors HX (X=F, Cl, Br, CN, NC, CCH, OH). For all complexes we find three different minima, two hydrogen bonded minima (to the Be or O atoms), and one weak beryllium bonded minimum.

Understanding the coupling of non-metallic heteroatoms to CO from a Conceptual DFT perspective.

Context: A Conceptual DFT (CDFT) study has been carry out to analyse the coupling reactions of the simplest amine (CHNH), alcohol (CHOH), and thiol (CHSH) compounds with CO to form the corresponding adducts CHNHCOH, CHOCOH, and CHSCOH. The reaction mechanism takes place in a single step comprising two chemical events: nucleophilic attack of the non-metallic heteroatoms to CO followed by hydrogen atom transfer (HAT). According to our calculations, the participation of an additional nucleophilic molecule as HAT assistant entails important decreases in activation electronic energies.

Striking Borane Planarization in the Thermal Rearrangement (η-CH)Fe(η-BH)→(η-CH)Fe(η-BH).

In 1977 Weiss and Grimes, by means of mass spectrometry and H and B NMR spectroscopy, proposed two structures (I and II) for the ferraborane (η-CH)Fe(BH), isoelectronic with ferrocene. In this work, by means of high-level quantum-chemical computations, we confirm the experimental structures of the two isomers with their corresponding energies, and assign the reported H and B NMR chemical shifts. A striking result from this study is the planarization (3D→2D) of the BH ligand - an unknown isolated anion, isoelectronic with aromatic cyclopentadienyl anion CH - when attached to the (η-CH)Fe moiety, thus resulting in a more stable ferraborane isomer II.