Reactions of Half-Sandwich Ethene Complexes of Rhodium(I) toward Iodoperfluorocarbons: Perfluoro-alkylation or -arylation of Coordinated Ethene versus Oxidative Addition

Perfluoroalkylation or perfluoroarylation of coordinated ethene takes place when complexes [Rh­(η⁵-Cp*)­(η²-C₂H₄)₂] or [Rh­(η⁵-Cp*)­(η²-C₂H₄)­(PR₃)] react with IR_F, to give complexes [Rh­(η⁵-Cp*)­(CH₂CH₂R_F)­(μ-I)]₂ (R_F = CF­(CF₃)₂ (<b>1a</b>), CF­(CF₃)­CF₂CF₃ (<b>1b</b>), or C­(CF₃)₃ (<b>1c</b>)) and [(η⁵-Cp*)­IRh­(μ-I)₂Rh­(η⁵-Cp*)­(CH₂CH₂R_F)] (<b>2a</b>–<b>c</b>), or [Rh­(η⁵-Cp*)­(CH₂CH₂R_F)­I­(PR₃)] (R = Me, R_F = CF­(CF₃)₂ (<b>3a</b>), C­(CF₃)₃ (<b>3c</b>), C₆F₅ (<b>3d</b>); R = Ph, R_F = CF­(CF₃)₂ (<b>3a</b>′), CF₂C₆F₅ (<b>3e</b>′)), respectively. Bridge splitting reactions of <b>1a</b>, <b>1b</b>, or <b>1c</b> with phosphines afford complexes [Rh­(η⁵-Cp*)­(CH₂CH₂R_F)­I­(PR₃)] (<b>3a</b>, <b>3a</b>′, <b>3c</b>; R_F = CF­(CF₃)₂, R = ^<i>i</i>Pr (<b>3a</b>″); R_F = CF­(CF₃)­CF₂CF₃, R = Me (<b>3b</b>), Ph (<b>3b</b>′)). In contrast, oxidative addition dominates over addition to ethene in the reactions of [Rh­(η⁵-Cp*)­(η²-C₂H₄)­(PMe₃)] with IR_F (R_F = CF₂C₆F₅, ^<i>n</i>C₃F₇, ^<i>n</i>C₄F₉, CFCF₂) and in the reaction of [Rh­(η⁵-Cp)­(η²-C₂H₄)­(PMe₃)] with I^<i>n</i>C₄F₉, affording complexes of the type [Rh­(η⁵-C₅R₅)­(R_F)­I­(PMe₃)] (<b>4e</b>–<b>h</b> and <b>5</b>, respectively). The reaction of [Rh­(η⁵-Cp*)­(η²-C₂H₄)­(PR₃)] with ICF­(CF₃)­CF₂CF₃ gives a mixture of <i>cis</i>- and <i>trans-</i>octafluoro-2-butene as the main fluoroorganic reaction product. Evidence for the intermediacy of R_F^– anions in these reactions has been obtained. <b>3a</b>′ reacts with AgOTf (OTf = O₃SCF₃) and XyNC or CO to give complexes [Rh­(η⁵-Cp*)­{CH₂CH₂CF­(CF₃)₂}­(CNXy)­(PPh₃)]­OTf (<b>6</b>) or [Rh­(η⁵-Cp*)­{C­(O)­CH₂CH₂CF­(CF₃)₂}­(CO)­(PPh₃)]­OTf (<b>7</b>), respectively. Complex [Rh­(η⁵-Cp*)­I­(py)­(PMe₃)]­BF₄ (<b>8</b>) was obtained either by reaction of (1) [Rh­(η⁵-Cp*)­(η²-C₂H₄)­(PMe₃)] with [I­(py)₂]­BF₄ or (2) [Rh­(η⁵-Cp*)­I₂(PMe₃)] with AgBF₄ and py. The crystal structures of <b>1a</b>, <b>1b</b>, <b>3c</b>,<b> 4g</b>,<b> 7</b>, and <b>8</b> have been determined