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Perfluoroalkylation of Coordinated Ethene in Rh(I) and Ir(I) Complexes. Catalytic Addition of Iodoperfluoroalkanes to Ethene

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journal contribution
posted on 21.03.2017, 12:04 by María Blaya, Delia Bautista, Juan Gil-Rubio, José Vicente
The complexes [M­(η5-Cp*)­(η2-C2H4)2] (M = Rh, Ir) react with iodoperfluoroalkanes to give [M­(η5-Cp*)­(CH2CH2RF)­(μ-I)]2 (main product) and [M­(η5-Cp*)­(CH2CH2RF)­(μ-I)2M­(η5-Cp*)­I] (RF = t-C4F9, M = Ir; RF = c-C6F11, M = Ir, Rh). Similarly, the complexes [M­(η5-Cp*)­(η2-C2H4)­(PPh3)] react with iodoperfluoroalkanes to give [M­(η5-Cp*)­(CH2CH2RF)­I­(PPh3)] (M = Ir, RF = t-C4F9, i-C3F7; M = Rh, RF = t-C4F9). Evidence for the generation of the heptafluoroisopropyl carbanion in the reaction of [Ir­(η5-Cp*)­(η2-C2H4)­(PPh3)] with I-i-C3F7 was obtained, which suggests that the reaction is initiated by the transfer of two electrons from the Ir­(I) complex to the iodoperfluoroalkane. The iodo-bridged complexes react with PPh3 to give [M­(η5-Cp*)­(CH2CH2RF)­I­(PPh3)] (M = Ir, RF = t-C4F9, c-C6F11; M = Rh, RF = c-C6F11). The complexes [Ir­(η5-Cp*)­(CH2CH2RF)­I­(PPh3)] (RF = c-C6F11, i-C3F7) react with AgOTf to give [Ir­(η5-Cp*)­H­(η2-CH2CHRF)­(PPh3)]­OTf. The analogous reaction of [Ir­(η5-Cp*)­(CH2CH2-t-C4F9)­I­(PPh3)] gives CH3CH2-t-C4F9 and [Ir­(η5-Cp*)­(η2-o-C6H4PPh2)]­OTf, which reacts with PPh3 to give [Ir­(η5-Cp*)­(η2-o-C6H4PPh2)­(PPh3)]­OTf. This cyclometalated complex and its analogue [Ir­(η5-Cp*)­(η2-o-C6H4PPh2)­(P­(p-Tol)3)]­OTf are also prepared by the reaction of [Ir­(η5-Cp*)­(Me)­Cl­(PPh3)] with AgOTf and PPh3 or P­(p-Tol)3. The derivatives [Ir­(η5-Cp*)­(CH2CH2RF)­(PPh3)­L]­OTf (L = CO, RF = c-C6F11, i-C3F7; L = PPh3, RF = i-C3F7) are isolated in the reactions of the Ir hydrido alkene complexes with CO or PPh3. The reactions of [Rh­(η5-Cp*)­(CH2CH2RF)­I­(PR3)] (R = Me, RF = i-C3F7, n-C4F9, t-C4F9; R = Ph, RF = i-C3F7, t-C4F9, c-C6F11) with AgOTf afford unstable triflato complexes that decompose to give CH2CHRF, but in the presence of PR3 the complexes [Rh­(η5-Cp*)­(CH2CH2RF)­(PR3)2]­OTf (R = Ph, RF = i-C3F7, t-C4F9, c-C6F11; R = Me, RF = i-C3F7, t-C4F9) were formed. When R = Ph, these complexes are unstable and decompose quantitatively to give [Rh­(η5-Cp*)­H­(PPh3)2]­OTf and CH2CHRF. Complexes of the type [M­(η5-Cp*)­(η2-C2H4)2] (M = Rh, Ir) and [Rh­(η5-Cp*)­(CH2CH2RF)­I­(L)] are initiators for the radical addition of IRF to ethene.