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A new mechanism of nucleophilic vinylic substitution and unexpected products in the reaction of chlorotrifluoroethylene with [Re(CO)5]Na and [CpFe(CO)2]K
Authors:PK Sazonov  IP Beletskaya
Institution:a Moscow State University, Chemistry Department, Leninskie Gory 1, GSP-2, Moscow 119992, Russian Federation
b A.N. Nesmeyanov Institute of Organoelement Compounds (INEOS), Russian Academy of Sciences, Vavilov Street 28, Moscow 119991, Russian Federation
Abstract:The mechanism of chloride substitution in CF2double bond; length as m-dashCFCl with Re(CO)5] and CpFe(CO)2] anions is investigated experimentally and theoretically. The substitution reaction begins with the nucleophile addition to CF2double bond; length as m-dashCFCl producing the carbenoid anion MCF2CFCl] (A) (M = Re(CO)5, CpFe(CO)2). This is shown by trapping the intermediate A with electrophiles - proton donor (t-BuOH) to give MCF2CFClH or with CF2double bond; length as m-dashCFRe(CO)5 to give acylmetallate III, and by the formation of the substitution products CF2double bond; length as m-dashCFM from the anion A, generated by the deprotonation of MCF2CFClH with t-BuOK. 1,2-Shift of metal carbonyl group concerted with the α-elimination of chloride anion is proposed as the transformation pathway of carbenoid A into CF2double bond; length as m-dashCFM. A competing process of carbene insertion into Fe-Ctriple bond; length of mdashO bond is proposed to explain the formation of Image (XI). The feasibility of these two pathways is confirmed by DFT (B3LYP/SDD and 6-31G) calculations of the carbenes MCF2CF:] and carbenoid anions MCF2CFCl]. Transition states (TS) for 1,2-shift (+3.2 kcal/mol) and for nucleophilic addition at Ctriple bond; length of mdashO ligand (+5.4 kcal/mol) are located for (CO)5ReCF2CFCl], but only one TS corresponding to carbene insertion into Fe-Ctriple bond; length of mdashO bond (+2.1 kcal/mol) is located for (CO)2CpFeCF2CFCl]. The formation of other newly observed products, F(CO)CHFRe(CO)5 (V) and Cp(CO)2FeCtriple bond; length of mdashCFeCp(CO)2 (VIII) is also discussed.
Keywords:Transition metal carbonyl anions  SNV reactions  1  2-Shift (migration)  Carbenoids  Iron  Rhenium  DFT calculations
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