Perfluoroalkylation of Coordinated Ethene in Rh(I) and Ir(I) Complexes. Catalytic Addition of Iodoperfluoroalkanes to Ethene
dataset
posted on 2017-03-21, 12:04 authored by María Blaya, Delia Bautista, Juan Gil-Rubio, José VicenteThe 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-CH2CHRF)(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 CH2CHRF, 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 CH2CHRF. 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.
