Ring contraction of metallabenzooxirene to metal carbonyl complexes – a comparative study with the Wolff rearrangement of oxirene and benzooxirene

Abstract

A detailed quantum mechanical study on the role of transition metal fragments towards the epoxidation reaction of metallabenzynes (1M, M = Fe, Ru, Os) to give metallabenzyne epoxide or metallabenzooxirene (2M), followed by the Wolff type 1,2-rearrangement to give metal carbonyls (4M), has been carried out at the M06/def2-TZVPP//BP86/def2-SVP level of theory. The epoxide or oxirene product (2A) of linear alkynes like acetylene is unstable and converts to a ketene (4A) by highly exothermic (-78.7 kcal mol) Wolff rearrangement via an oxocarbene (3A) intermediate. The epoxide product of cyclic alkynes like benzyne (2C) is comparatively more stable than benzooxocarbene (3C), yet it undergoes rearrangement to cyclopentadienylketene (4C) through Wolff type ring contraction reactions (-65.3 kcal mol). The replacement of one of the carbyne carbons in benzyne by 14 VE metal fragment M(PH)Cl, M = Fe, Ru and Os enhances the stability of the 18 VE metallabenzyne epoxide product (2M, -88.1 kcal mol for 2Fe, -87.2 kcal mol for 2Ru and -82.8 kcal mol for 2Os) as compared to the 16 VE metallacyclohexadienone (3M). The ring contracted 18 VE product of 2M is a carbonyl bridged metallacyclopentadienyl complex (4M, M = Fe, Ru and Os). Even though this interconversion is thermodynamically favourable, it involves a high-energy barrier (19.3, 28.1 and 27.9 kcal mol for 2Fe, 2Ru and 2Os, respectively). However, the hepta-coordinated (5M) terminal metallacyclopentadienyl carbonyl analogues of ketene (4A/4C) are not minima on the potential energy surface.

Study on Removal Mechanism for Copper Cyanide Complex Ions in Water: Ion Species Differences and Evolution Process

“…Then, the whole optimization was carried out in the gas phase, the frequency corresponding to the optimized structure was calculated and the position was determined to be the minimum. M062x/def2tzvp was used to calculate thermodynamic energies and includes the empirical dispersion correction D3BJ to describe dispersion effects [ 44 , 45 , 46 ]. An implicit water solvation model is used to simulate the solvent environment [ 47 ].…”

Inhibition Role of Solvation on the Selective Extraction of Co(II): Toward Eco-Friendly Separation of Ni and Co

“…Then, the entire optimization was carried out in the gas phase, and the corresponding frequencies of the optimized structures were calculated to confirm that the position was the minimum. M06/def2tzvp was used for the calculation of thermodynamic energy, , and the empirical dispersion correction D3BJ was included to describe the dispersion effect . The solvation model based on the density model (ε water = 78.4, ε toluene = 2.38) was used to simulate the solvent environment.…”