Written by: Shawn.Adams2@unt.edu
Congratulations to Catherine Moulder and Kristina Kafle, Chemistry graduate and undergraduate
students working with Dr. Thomas Cundari, for having their article "Tungsten-Ligand
Bond Strengths for 2p Elements Including σ- and π-Bond Strength Components, A Density
Functional Theory and ab Initio Study" chosen as the cover for the September 19 edition
of the Journal of Physical Chemistry A. Congratulations to Kristina Kafle and Catherine Moulder for designing the cover
art and Kristina for hand-drawing it.
Abstract: Three WVI crystal structures with multifarious metal-ligand bond types are used to
theoretically predict homolytic metal-element bond enthalpies with 11 popular DFT
functionals, MP2 wave function methods, and four common valence basis set/pseudopotentials
in order to evaluate the accuracy and precision of the resultant bond enthalpy data.
To our knowledge, for the first time, estimates of component metal-ligand σ- and π-bond
strengths are computed. The WE (E = C, N, O) bond enthalpies have the consistent trend
σ > second π > first π. In contrast, the element-element BDE trend for the 2p homologues
is second π > first π > σ for nitrogen and oxygen, and σ > first π > second π for
carbon. These differences may underpin the differences in stability trends and thus
reactivity behavior for metal-element multiple bonds as compared to the element-element
multiple bonds, and metal-element triple bonds versus their corresponding double bonded
counterparts. For example, Odom et al. show that MeI nucleophilically attacks at the imide (M-N) rather than the nitride
(M = N) ligand; the relative π-bond strengths derived herein provide a thermodynamic
rationalization for this site preference. In this study, it is deduced from the calculated
thermodynamics that the W-oxo ligand is more congruous with a triple bond than a double
bond, consistent with the bonding model set forth in the seminal 1961 Ballhausen-Gray
paper.
You can view the article here.