Unique bonding pattern and resulting bond stretch isomerism in Be32−

Abstract

The bond‐stretch isomers are characterized by a principal change in the bond‐length with the rest of the molecule being unaltered. The electronic structure regulates the bond stretch isomerism phenomenon in Be32− which has been investigated with density functional theory, ab initio CASSCF, highly efficient n‐electron valence state perturbation theory and multireference configuration interaction calculations. Two isomers are distinguished on different potential energy surfaces and the corresponding avoided crossing is also studied in details. The bonding pattern in two isomers are analysed through adaptive natural density partitioning analysis and quantum theory of atoms in molecules analysis. The bonds in both the isomers primarily involve the 2p orbitals, which overlap face‐to‐face in long‐bond isomer. Whereas, in‐plane π‐bonding occurs at the short‐bond isomer leading to unusual bent bond. © 2015 Wiley Periodicals, Inc.

Lifetimes of Be32– and Mg32– Cluster Dianions

“…We focus primarily on D 3 h symmetrical structures at geometries between the neutral and the anion as the lowest electronic states of both neutral Be 3 and Be 3 – are trigonal planar and the same is true for the corresponding Mg species. Moreover, we investigate the symmetric breathing mode of Be 3 , Be 3 – , and Be 3 2– over a range that covers some of the structures discussed in refs − and .…”

“…The S σσ and S ππ states have been interpreted as σ and π aromatic, and various properties of these two states and of the triplet state have been investigated for the isolated dianions − as well as for metal clusters such as NaBe 3 – or Na 2 Mg 3 , which feature the two trimer dianions as structural units. ,, In this context, the S ππ state can be characterized as a 2π aromatic system as the bonding p−π a 2 ″ orbital is doubly occupied. Similarly, the S σσ state can be said to possess σ-aromatic character as the bonding p−σ a 1 ′ orbital is doubly occupied.…”

“…Let us note that the isolated-dianion perspective may explain conflicting results about the electronic ground states and equilibrium structures of the isolated dianion (see, for example, refs − ). Electronically metastable states can be understood as discrete states of an ( N + 1)-electron system that is embedded in and interacts with a continuum of states describing the N -electron system plus a free electron.…”

Switchable dual bonding nature in silabicyclo[1.1.0]butanes that exhibit bond stretch isomerism

“…One of such phenomena is the bond stretch isomerism, the isomer where more than one stable configuration of the same molecule exists with only major distinct difference in the bond length. Many instances of bond stretch isomerization have been theorized or reported for organic, main group elements, and transition metal compounds . Among such structures is the silicon analogues of bicyclo[1.1.0]butane (Scheme a).…”

Theoretical evidence for bond stretch isomerism in Grubbs olefin metathesis

“…From a theoretical point of view, isomers of BSI must be inter‐convertible through a well‐defined transition state. To date, most of the reported examples of BSI are hypothetical models, and not many examples are known characterized by crystallography techniques . Furthermore, there is no report on the observation of BSI in a catalytic reaction which could play a decisive role in the reaction mechanism.…”