Effect of Transition Metal Fragments on the Reverse Fritsch–Buttenberg–Wiechell Type Ring Contraction Reaction of Metallabenzynes to Metal–Carbene Complexes

Abstract

Metallabenzynes (1M), contrary to their organic analogues, benzynes, undergo ring-contraction to metal-carbene complexes (2M) via a reverse Fritsch-Buttenberg-Wiechell (FBW) type rearrangement. A detailed computational quantum mechanical study has been carried out to understand the effect of different third row transition metal fragments (MLL'; M = W, Re, Os, Ir, Pt; L/L' = PH, Cl, CO) on the stability of metallabenzynes and their reactivity toward reverse FBW type rearrangement. Our results indicate that the late transition metal fragments Ir(PH)Cl and PtCl prefer 16 VE metal-carbene complex (2M), while the middle transition metal fragments W(PH), Re(PH)Cl, and Os(PH)Cl prefer metallabenzyne (1M). This can be attributed to the reduced overlap between the transition metal fragment MLL' and organic fragment CH in metallabenzyne 1M when M changes from W to Pt. Furthermore, the presence of a π-accepting ligand CO on the metal fragment makes the conversion of 1M to 2M more feasible.

Synthesis, TDDFT Calculations and Biological Evaluation of Dicationic Porphyrins as Groove Binders and Antimicrobial Agents

“…It has been shown earlier that the M06/Def2‐TZVPP//BP86/Def2‐SVP level of theory gives reliable geometries, electron density distributions, and spectroscopic properties of tetrapyrrolic macrocycles and other transition‐metal complexes [40–46] . Our earlier computational studies [47,48] on metalloporphyrins also substantiated that the combination of BP86 functional with a def2‐SVP basis set is capable of providing accurate geometry with the experimental crystal data.…”