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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) 3 , 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. Further characterization of the interactions using a topological analysis of the electron density and Symmetry Adapted Perturbation Theory (SAPT) provide insight into the nature of these interactions. Overall these results highlight the capability of certain beryllium compounds to act as either a weak Lewis acid or, unconventionally, a Lewis base whose basicity towards hydrogen bonding is comparable to that of π systems., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

A theoretical study of the complexes formed by carbene like Al(I), Ga(I), In(I) and Tl(I) compounds with hydrogen bond donors (HBD), XH (HCCH, HSH,HOH, HCN, HCl, HBr, HF, and HNC) have been carried out at MP2 computational level. The isolated triel(I) compounds show a negative region of the molecular electrostatic potential region associated with the triel atom suitable to interact with electron deficient groups. This region is associated to a lone pair based on the ELF analysis and to the location of the HOMO orbital. The complexes are similar to those found in nitrogen heterocyclic carbenes (NHC) with HBD. In addition, the oxidative addition reactions of those complexes to yield the corresponding valence III compounds have been characterized. The Al(III) compounds are much more stable than the corresponding Al(I) complexes. However, the stability of the triel(III) compounds decreases with the size of the triel atom and for the thallium derivatives, the Tl(I) complexes are more stable than the Tl(III) compounds in accordance with the number of the structures found in the CSD. The barrier of the TS connecting the triel(I) and triel(III) systems increases with the size of the triel atoms., (© 2024 Wiley-VCH GmbH.)

We have reported in the last years the strong effect that Be- and Mg-containing Lewis acids have on the intrinsic properties of typical bases, which become acids upon complexation. In an effort to investigate these changes when the Be and Mg derivatives form clusters of increasing size, we have examined the behavior of the (MX 2 ) n (M = Be, Mg; X = H, F; n = 1, 2, 3) clusters when they interact with ammonia, methanimine, hydrogen cyanide and pyridine, and with their corresponding deprotonated forms. The complexes obtained at the M06-2X/aug-cc-pVTZ level were analyzed using the MBIE energy decomposition formalism, in parallel with QTAIM, ELF, NCIPLOT and AdNDP analyses of their electron density. For n = 1 the interaction enthalpy for the different families of monomers, Be (Mg) hydrides and Be (Mg) fluorides, follows the same trend as the intrinsic basicity of the base that interacts with them. This interaction is greatly reinforced after the deprotonation of the base, resulting in a significant enhancement of the intrinsic acidity of the corresponding MX 2 -Base complex. For (MX 2 ) 2 clusters a further reinforcement of the interaction with the base is observed, this reinforcement being again larger for the deprotonated complexes. However, the concomitant increase of their intrinsic acidity is one order of magnitude larger for hydrides than for fluorides. Unexpectedly, the cyclic conformers (MX 2 ) 3 , which are more unstable than the linear ones, become the global minima after association with the base and the same is true for the deprotonated complex. Accordingly, a further increase of the intrinsic acidity of the (MX 2 ) 3 -Base complexes with respect to the (MX 2 ) 2 -Base ones is observed. This effect is maximum for (MgF 2 ) 3 clusters, to the point that the (MgF 2 ) 3 -Base complexes become more acidic than nitric acid, the extreme case being the cluster (MgF 2 ) 3 -NCH, whose acidity is higher than that of perchloric acid., (© 2024 The Authors. Journal of Computational Chemistry published by Wiley Periodicals LLC.)

In 1977 Weiss and Grimes, by means of mass spectrometry and 1 H and 11 B NMR spectroscopy, proposed two structures (I and II) for the ferraborane (η 5 -C 5 H 5 )Fe(B 5 H 10 ), 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 1 H and 11 B NMR chemical shifts. A striking result from this study is the planarization (3D→2D) of the B 5 H 10 - ligand - an unknown isolated anion, isoelectronic with aromatic cyclopentadienyl anion C 5 H 5 - - when attached to the (η 5 -C 5 H 5 )Fe + moiety, thus resulting in a more stable ferraborane isomer II., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Context: A Conceptual DFT (CDFT) study has been carry out to analyse the coupling reactions of the simplest amine (CH 3 NH 2 ), alcohol (CH 3 OH), and thiol (CH 3 SH) compounds with CO 2 to form the corresponding adducts CH 3 NHCO 2 H, CH 3 OCO 2 H, and CH 3 SCO 2 H. The reaction mechanism takes place in a single step comprising two chemical events: nucleophilic attack of the non-metallic heteroatoms to CO 2 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. In such cases, the formation of a six-membered ring in the transition state (TS) reduces the angular stress with respect to the non-assisted paths, characterised by four-membered ring TSs. Through the analysis of the energy and reaction force profiles along the intrinsic reaction coordinate (IRC), the ratio of structural reorganisation and electronic rearrangement for both activation and relaxation energies has been computed. In addition, the analysis of the electronic chemical potential and reaction electronic flux profiles confirms that the highest electronic activity as well as their changes take place in the TS region. Finally, the distortion/interaction model using an energy decomposition scheme based on the electron density along the reaction coordinate has been carried out and the relative energy gradient (REG) method has been applied to identify the most important components associated to the barriers., Methods: The theoretical calculation were performed with Gaussian-16 scientific program. The B3LYP-D3(BJ)/aug-cc-pVDZ level was used for optimization of the minima and TSs. IRC calculations has also been carried out connecting the TS with the associated minima. Conceptual-DFT (CDFT) calculations have been carried out with the Eyringpy program and in-house code. The distortion/interaction model along the reaction coordinate have used the decomposition scheme of Mandado et al. and the analysis of the importance of each components have been done with the relative energy gradient (REG) method., (© 2024. The Author(s).)

The reactivity of B 3 N 3 -doped hexa-cata-hexabenzocoronene (B 3 N 3 -NG), Al 3 N 3 -NG, B 3 P 3 -NG and Al 3 P 3 -NG, models of doped nanographenes (NGs), towards carbon dioxide was studied with density functional theory (DFT) calculations at the M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G* level of theory. The NG systems exhibit a poly-cyclic poly-frustrated Lewis pair (FLP) nature, featuring multiple Lewis acid/Lewis base pairs on their surface enabling the capture of several CO 2 molecules. The capture of CO 2 by these systems was investigated within two scenarios: (A) sequential capture of up to three CO 2 molecules and (B) capture of CO 2 molecules in the presence of a sodium cation. The resulting adducts were analyzed in terms of the activation barriers and relative stabilities. The presence of aluminium atoms changes the asynchrony of the reaction favoring the aluminium-oxygen bond and influences the regioselectivity of the multi-capture. A cooperative effect is predicted due to π-electron delocalization, with the sodium cation stabilizing the stationary points and favoring the addition of CO 2 to the NGs.

High-energetic materials belong to two main classes: propellants and explosives. The still rather unexplored family of 1,3,5,2,4,6-trioxatriazinanes, N 3 O 3 R 3 , has a representative of each class. We have selected three compounds, R = H, R = CH 3 and R = NO 2 , this last compound being known as TNTOTA, "trinitro-trioxa-triazinane". Of these compounds we have studied the conformational analysis, the nitrogen inversion, the heats of formation, and the dissociation reaction into the three monomers. In addition, the corresponding 1,3,2,4-dioxadiazetidines (N 2 O 2 R 2 ) have also been studied., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

A comprehensive comparison between known benzene mono-substituted compounds R-Ph and the corresponding isoelectronic unknown R-cyclohexaborane(12) molecules is carried out from a geometric and electronic structure point of view, with R={H, BH 2 , CH 3 , NH 2 , OH, F ; AlH 2 , SiH 3 , PH 2 , SH, Cl ; NO 2 , OCH 3 }. We suggest new chemical names for the 2D borane compounds and analyze the geometric and electronic structure carbon vs. boron comparatives by means of HOMO-LUMO gaps, bonding schemes, electron density topological properties and predicted NMR chemical shifts. The predictions on the properties in planar hexagonal cyclic boranes may help in the design of synthesis procedures for these yet-unkown compounds., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

The isolated (pyridin-2-ylmethyl)triel derivatives (triel=B, Al and Ga) show an intramolecular N⋅⋅⋅Tr triel bond as shown by compounds found in the Cambridge Structural Database and DFT calculations. The possibility to use them as masked frustrated Lewis pairs (mFLP) has been explored theoretically concerning their reaction with CO 2 . The adduct formation proceeds in two steps. In the first one, the (pyridin-2-ylmethyl)triel derivatives break the intramolecular N⋅⋅⋅Tr bond assisted by CO 2 and in the second step the adduct is formed with Tr-O and N-C covalent bonds. The corresponding energy minima and transition states (TS) of the reaction have been characterized and analyzed. The distortion/interaction model analysis of the stationary points indicates that the whole process can be divided in two parts: reorganization of the mFLP in the first steps of the reaction while the reaction with CO 2 (associated to the distortion of this molecule) is more important in the formation of the final adduct. In all cases studied, the final products are more stable than the starting molecules that combine with reasonable TS energies indicating that these reactions can occur., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

A theoretical study of the interaction between melamine and CO 2 was carried out using density functional theory (DFT) with the B3LYP-D3(BJ)/aug-cc-pVTZ level of theory. The presence of anions interacting with melamine transforms the weakly bonded tetrel complexes into adducts. Thus, melamine acts as an FLP (frustrated Lewis pair) with acid groups (NHs as hydrogen bond donors) and a base group (N of the triazine ring). The application of the relative energy gradient formalism (REG) along the reaction coordinate has demonstrated that the ability of the melamine-anion systems to capture CO 2 is linked to its capacity to polarize the CO 2 molecule. These results have been confirmed by placing the melamine:CO 2 complex in a uniform electric field with different strengths.