The present review provides both a summary and outlook on the exciting field of BODIPYs in polymer chemistry.

Three W VI 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 σand 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.

There are two primary foci in this research on WE (E = Si, P, and S) bonds: prediction of their bond dissociation enthalpies (BDEs), including σ- and π-bond energy components, and assessing the uncertainty of these BDE predictions for levels of theory commonly used in the literature. The internal standards for computational accuracy include metal–element bond lengths (mean absolute error = 1.8 ± 1.2%), main group homolog BDEs versus higher levels of ab initio theory (W1U and G4 BDEs, R 2 = 0.98), and DLPNO-CCSD­(T)/def2-QZVPP calculations for metal–ligand BDEs (R 2 = 0.88). The WSi first π-bond is underreported for density functional theory (DFT)/MP2 methods versus DLPNO-CCSD­(T), while the latter shows negligible strength for the W;Si second π-bond, consistent with the literature. This research highlights clear issues with the underlying assumptions required for the use of perturbation theory methods for the fragments derived from W–P homolysis. The difficulties associated with modeling the metal thermochemistry with DFT (and MP2) levels of theory are manifest in the broad standard deviations observed. However, the average BDEs found using 48 popular DFT and MP2 levels of theory are reliable, 10.8 ± 6.8% mean absolute error (with W–P removed) versus DLPNO-CCSD­(T), with the caveat that the individual basis set/pseudopotential/valence basis set combination can vary wildly. Analysis of the absolute error percentages with respect to the level of theory indicates little benefit to going higher on Jacob’s Ladder, as simpler methods have lower error versus high-level ab initio techniques such as G4 and DLPNO-CCSD­(T).