Ab Initio Search for Global Minimum Structures of the Novel B3Hy (y=4−7) Neutral and Anionic Clusters

Superhalogens: A Bridge between Complex Metal Hydrides and Li Ion Batteries

Complex metal hydrides and Li ion batteries play an integral role in the pursuit of clean and sustainable energy. The former stores hydrogen and can provide a clean energy solution for the transportation industry, while the latter can store energy harnessed from the sun and the wind. However, considerable materials challenges remain in both cases, and research for finding solutions has traditionally followed parallel paths. In this Perspective, I show that there is a common link between these two seemingly disparate fields that can be unveiled by studying the electronic structure of the anions in complex metal hydrides and in electrolytes of Li ion batteries; they are both superhalogens. I demonstrate that considerable progress made in our understanding of superhalogens in the past decade can provide solutions to some of the materials challenges in both of these areas.

Unexpected cluster formation upon hydroboration of a neutral diborene with 9-BBN

The reaction of the neutral, base-stabilised diborenes 1a,b with the well-known hydroboration reagent 9-borabicyclo[3.3.1]nonane (9-BBN) is presented. This leads to the formation of a nonclassical structural motif with a B3 core concomitant with the cleavage of a B-C bond. This compound has been characterised in solution and by X-ray crystallography. According to Wade's rules these rare B3 clusters follow the arachno classification (2n + 6 electrons) and represent doubly base-stabilised B3H5 analogues.

Photoelectron spectroscopy of boron-gold alloy clusters and boron boronyl clusters: B3Au(n)(-) and B3(BO)n(-) (n = 1, 2)

Photoelectron spectroscopy and density-functional theory are combined to study the structures and chemical bonding in boron-gold alloy clusters and boron boronyl clusters: B3Au(n)(-) and B3(BO)n(-) (n = 1, 2). Vibrationally resolved photoelectron spectra are obtained for all four species and the B-Au and B-BO clusters exhibit similar spectral patterns, with the latter species having higher electron binding energies. The electron affinities of B3Au, B3Au2, B3(BO), and B3(BO)2 are determined to be 2.29 ± 0.02, 3.17 ± 0.03, 2.71 ± 0.02, and 4.44 ± 0.02 eV, respectively. The anion and neutral clusters turn out to be isostructural and isovalent to the B3H(n)(-)∕B3H(n) (n = 1, 2) species, which are similar in bonding owing to the fact that Au, BO, and H are monovalent σ ligands. All B3Au(n)(-) and B3(BO)n(-) (n = 1, 2) clusters are aromatic with 2π electrons. The current results provide new examples for the Au∕H and BO∕H isolobal analogy and enrich the chemistry of boronyl and gold.

Computational study of the initial stage of diborane pyrolysis

The rate constants for the association of two boranes to form diborane are investigated using several methods. The most sophisticated method is the variable reaction coordinate-variational transition state theory (VRC-VTST) which has been developed to handle reactions with no enthalpic barriers. The calculated rate constant of 8.2 × 10(-11) cm(3)·molecule(-1)·s(-1) at 545 K is in good agreement with experiment. The rate constant was also computed using conventional VTST with the G4 composite method. Two variations of the multistep mechanisms for diborane pyrolysis are presented. One is initiated by the step B2H6 ⇄ 2 BH3 while the other begins with 2 B2H6 ⇄ B3H9 + BH3 as the initial elementary step. Both variations are 3/2 order in diborane and have the same activation energy (G4, 28.65 kcal/mol at 420 K). In contrast, the traditional mechanism involving a B3H9 intermediate with C3v symmetry has a higher activation energy (33.37 kcal/mol). The two variations involve a C2-symmetry penta-coordinate B3H9 structure that, while an electronic minimum, is not a stationary point on the free energy path between B2H6 + BH3 → B3H7 + H2. While the calculated activation barrier is higher than the recently determined experimental barrier, the variation in reported values is large (22.0-29.0 kcal/mol). We discuss possible sources of disagreement between experiment and theory.