Nucleophilicity of metal carbonyl anions in vinylic substitution reactions |
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| Authors: | Petr K Sazonov Galina A Artamkina Irina P Beletskaya |
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| Institution: | Chemistry Department, M.V. Lomonosov Moscow State University, Leninskie Gory 1, Moscow 119992, Russian Federation |
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| Abstract: | Second order rate constants are reported for the reactions of metal carbonyl anions (M(CO)nL]?) with several vinyl halides: PhCCl?C(CN)2, Z‐ and E‐Ph(CN)C?CHHal (Hal = Cl, Br) which follow the addition–elimination (AdNE) substitution mechanism. The obtained data show that the nucleophilic reactivity of M(CO)nL]? anions towards vinyl halides increases in the same order as in aliphatic SN2 reactions, but much more steeply, by 14 orders of magnitude in the row log{ }: CpFe(CO)2]? (～14), Re(CO)5]? (7.8), Mn(CO)5]? 2.1, CpW(CO)3]? (0.7) > CpMo(CO)3]? (0). A good correlation exists between nucleophilicities of M(CO)nL]? anions towards vinyl (sp2‐carbon) and alkyl halides (sp3‐carbon) with slope 2.7. The reactivity of M(CO)nL]? in a halogen–metal exchange process (with Z‐PhC(CN)?CHI) follows a similar ‘large’ scale as in the AdNE process. The nucleophilicity of M(CO)nL]? anions correlates better with their one‐electron oxidation potentials (Eox) than with their basicity (pKa of M(CO)nL]H). Copyright © 2008 John Wiley & Sons, Ltd. |
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| Keywords: | nucleophilicity metal carbonyl anions SNV nucleophilic vinylic substitution reaction mechanisms |
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