Computational Predictions of the Beryllium Analogue of Borole, Cp(+), and the Fluorenyl Cation: Highly Stabilized, non-Lewis Acidic Antiaromatic Ring Systems

Recent progress in beryllium organometallic chemistry

Beryllium possesses a unique amalgamation of characteristics, its electronegativity included, that not only make it a vital component in a wide range of technical sectors and consumer industries, but also make it an interesting candidate for forming covalently bonded compounds. However, the extremely toxic nature of beryllium, which can cause chronic beryllium disease, has limited the exploration of its chemistry, making beryllium one of the least studied (non-radioactive) elements. The development of selective chelating ligands, sterically encumbered substituents and, moreover, the boom of N-heterocyclic carbenes in organometallic chemistry and main group chemistry has revived the interest in beryllium chemistry. Therefore, some quite remarkable progress in the coordination and organometallic chemistry of beryllium has been made in the last two decades. For example, low oxidation state beryllium compounds, antiaromatic/aromatic beryllium compounds, where beryllium is involved in π-electron delocalization, and the isolation of beryllium-beryllium bonded species have all been achieved. This article provides an oversight over the recent developments in the organometallic chemistry of beryllium.

Isolation and Reactivity of an Antiaromatic s-Block Metal Compound

The concepts of aromaticity and antiaromaticity have a long history, and countless demonstrations of these phenomena have been made with molecules based on elements from the p, d, and f blocks of the periodic table. In contrast, the limited oxidation-state flexibility of the s-block metals has long stood in the way of their participation in sophisticated π-bonding arrangements, and truly antiaromatic systems containing s-block metals are altogether absent or remain poorly defined. Using spectroscopic, structural, and computational techniques, we present herein the synthesis and authentication of a heterocyclic compound containing the alkaline earth metal beryllium that exhibits significant antiaromaticity, and detail its chemical reduction and Lewis-base-coordination chemistry.

Photodetachment spectroscopy of the beryllium oxide anion, BeO. J Chem Phys 2017;146:054301. [PMID: 28178838 DOI: 10.1063/1.4974843]

The X²Σ⁺→X¹Σ⁺ anion to neutral ground state photodetachment of BeO^- has been studied by means of photoelectron velocity-map imaging spectroscopy in a newly constructed apparatus. Vibrational intervals, rotational constants, and the electron detachment threshold of BeO^- were determined for the first time. The small moment of inertia of beryllium oxide allowed for the observation of partially resolved rotational contours. Analyses of these contours provided evidence of several detachment channels resulting from changes in molecular rotational angular momenta of ΔN = 0, ±1, ±2, and ±3. The relative intensities of these detachment channels were found to be a function of the electron kinetic energy. Experimental results are compared to the predictions of high level ab initio calculations.

Theoretical strategies toward stabilization of singlet remote N-heterocyclic carbenes

Theoretical investigations predict that the singlet states of ylide-substituted remote carbenes are significantly stable and comparable to those of experimentally known NHCs. They are also found to be strongly σ-donating in nature as evident from an evaluation of the carbonyl stretching frequencies (νCO ) of their complexes with the [Rh(CO)2 Cl] fragment. NICS and QTAIM based bond magnetizability calculations indicate the presence of cyclic electron delocalization in majority of the molecules. © 2016 Wiley Periodicals, Inc.