antiaromaticity

Antiaromaticity-Promoted Activation of Dihydrogen with Borole Fused Cyclooctatetraene Frustrated Lewis Pairs: A Density Functional Theory Study

Aromaticity and frustrated Lewis pairs (FLP), two important concepts in chemistry, have attracted considerable attention from theoretical and experimental chemists. However, combining these two concepts together for H2 activation is less developed. Herein, we report a density functional theory study on antiaromaticity-promoted H2 splitting. The antiaromatic borole (as Lewis acid) and aromatic pyridine (as Lewis base) were introduced into the cyclooctetraene skeleton. Due to the geometric constraints, such systems can be classified as FLPs.

Predicting an Antiaromatic Benzene Ring in the Ground State Caused by Hyperconjugation

Benzene, the prototype of aromatics, has six equivalent C‐C bonds (1.397 Å), which are intermediate between a C‐C double bond and a C‐C single bond. For over 80 years, chemists have spent much effort on freezing a localized structure to obtain a distorted bond‐length alternating benzene ring in the ground state, leading to various localized trisannelated benzene rings. However, most of the central benzene rings are still aromatic or nonaromatic. Here we report an antiaromatic benzene ring caused by hyperconjugation.

Unexpected higher stabilisation of two classical antiaromatic frameworks with a ruthenium fragment compared to the osmium counterpart: origin probed by DFT calculations

Density functional theory (DFT) calculations were carried out to investigate the stability and aromaticity of metallapentalocyclobutadienes. The results reveal unexpected higher stabilisation achieved with a 3d ruthenium fragment compared to the 4d osmium counterpart. Moreover, direct 1–3 metal–carbon bonding in the metallabutadiene unit of these two complexes is negligible.

http://pubs.rsc.org/en/content/articlelanding/2015/cc/c5cc08291a#!divAbstract

Congratulations to Jingjing, Yulei, and Ke for their paper accepted in Chem. Commun.

Communication

Unexpected Higher Stabilisation of Two Classical Antiaromatic Frameworks with a Ruthenium Fragment over Osmium Counterpart: Origin Probed by DFT Calculations

Jingjing Wu,   Yulei Hao,   Ke An and   Jun Zhu  

Stabilizing Two Classical Antiaromatic Frameworks: Demonstration of Photoacoustic Imaging and the Photothermal Effect in Metalla-aromatics

Antiaromatic species are substantially less thermodynamically stable than aromatic moieties. Herein, we report the stabilization of two classical antiaromatic frameworks, cyclobutadiene and pentalene, by introducing one metal fragment through the first [2+2] cycloaddition reaction of a late-transition-metal carbyne with alkynes. Experimental observations and theoretical calculations reveal that the metal fragment decreases the antiaromaticity in cyclobutadiene and pentalene simultaneously, leading to air- and moisture-stable products.

Stabilization of anti-aromatic and strained five-membered rings with a transition metal

Anti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8π-electron anti-aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon.