A1 Refereed original research article in a scientific journal

Pyrazolium- and 1,2-Cyclopentadiene-Based Ligands as sigma-Donors: a Theoretical Study of Electronic Structure and Bonding




AuthorsPeuronen A, Hanninen MM, Tuononen HM

PublisherAMER CHEMICAL SOC

Publication year2012

JournalInorganic Chemistry

Journal name in sourceINORGANIC CHEMISTRY

Journal acronymINORG CHEM

Volume51

Issue4

First page 2577

Last page2587

Number of pages11

ISSN0020-1669

DOIhttps://doi.org/10.1021/ic202546a(external)


Abstract
A high-level theoretical investigation of 1,2-cyclopentadiene (4) was performed using density functional theory and wave function methods. The results reveal that, in contrast to earlier assumptions, the ground state of this ephemeral "allene" is carbene-like with a small diradical component. Furthermore, the electronic structure and chemistry of 4 are found to parallel that of 1,2,4,6-cycloheptatetraene: both molecules possess a low-lying excited singlet state with a closed-shell carbenic structure, enabling rich coordination chemistry. Energy decomposition analyses conducted for currently unknown metal complexes of 4 as well as those involving stable carbenes based on the pyrazolium framework (aka "bent allenes" or remote N-heterocyclic carbenes) indicate that all investigated ligands form particularly strong metal-carbon bonds. Most notably, without exocyclic pi-type substituents, 4 and pyrazolin-4-ylidenes are the strongest donor ligands examined, in large part because of the energy and shape of their highest occupied molecular orbital. As a whole, the current work opens a new chapter in the chemistry of 1,2-cyclopentadiene, which is hoped to spark renewed interest among experimentalists. In addition, results from the conducted bonding analyses underline that more emphasis should be placed on purely carbocyclic carbenes as unprecedented sigma-donor strengths can be realized through this route.



Last updated on 2024-26-11 at 13:27