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 |
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Authors: | PK Sazonov IP Beletskaya |
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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 |
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Abstract: | The mechanism of chloride substitution in CF2 CFCl with Re(CO)5]− and CpFe(CO)2]− anions is investigated experimentally and theoretically. The substitution reaction begins with the nucleophile addition to CF2 CFCl 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 CF2 CFRe(CO)5 to give acylmetallate III, and by the formation of the substitution products CF2 CFM 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 CF2 CFM. A competing process of carbene insertion into Fe-C O bond is proposed to explain the formation of (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 C O ligand (+5.4 kcal/mol) are located for (CO)5ReCF2CFCl]−, but only one TS corresponding to carbene insertion into Fe-C O 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)2FeC CFeCp(CO)2 (VIII) is also discussed. |
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Keywords: | Transition metal carbonyl anions SNV reactions 1 2-Shift (migration) Carbenoids Iron Rhenium DFT calculations |
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