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

Abstract

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, 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). Evidences of the generation of the heptafluoroisopropyl carbanion in the reaction of [Ir(η5-Cp*)(η2-C2H4)(PPh3)] with I-i-C3F7 were obtained, which suggest that the reaction is initiated by the 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). 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, that 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 reaction of [Ir(η5-Cp*)(Me)Cl(PPh3)] with AgOTf and PPh3 or P(p-Tol)3. 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 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 or Ir) or [Rh(η5-Cp*)(CH2CH2RF)I(L)] are initiators for the radical addition of IRF to ethene.