The reaction of AgBF4 and [Rh(COD)Cl]2 (COD=1,5‐cyclooctadiene) in presence of [NEt4][C5(CF3)5] afforded the fluorocarbon soluble complex [Rh(COD)(C5(CF3)5)] by salt metathesis. This complex represents the first example for a successful coordination of the weakly basic [C5(CF3)5]− ligand, since its first synthesis in 1980. In addition to [Rh(COD)(C5(CF3)5)] also the byproduct [Rh(COD)(C5(CF3)4H)] was isolated and fully characterized. Accompanying DFT studies showed that the interaction energy of the [C5(CF3)5]− ligand towards the 12‐electron fragment [Rh(COD)]+ is ≈70 kcal mol−1 lower in comparison to [C5(CH3)5]− due to reduced electrostatic interactions and weaker π‐donor properties of the ligand. The quantitative but reversible substitution of the [C5(CF3)5]− ligand by toluene, converting it into a weakly coordinating anion, experimentally proved the extraordinary weak bonding interaction.

Several cationic rhodium(I) complexes [Rh(COD)L2][C5(CF3)5] have been synthesized through substitution of the weakly bound [C5(CF3)5]– ligand from [Rh(COD)(C5(CF3)5)], further emphasizing its unique reactivity. Besides acetonitrile, pyridine derivatives with varying degrees...

Die Reaktion zwischen AgBF 4 und [Rh-(COD)Cl] 2 (COD = 1,5-Cyclooctadien) in Gegenwart von [NEt 4 ][C 5 (CF 3 ) 5 ] ergab den perfluorcarbonlöslichen Komplex [Rh(COD)(C 5 (CF 3 ) 5 )] durch Salzmetathese. Dieser Komplex stellt das erste Beispiel für eine erfolgreiche Koordination des schwach basischen [C 5 (CF 3 ) 5 ] À -Liganden, seit dessen Erstsynthese im Jahr 1980 dar. Zusätzlich zu [Rh(COD)(C 5 (CF 3 ) 5 )] wurde das Nebenprodukt [Rh(COD)(C 5 (CF 3 ) 4 H)] isoliert und vollständig charakterisiert. Begleitende DFT-Rechnungen zeigen, dass die Interaktionsenergie des [C 5 (CF 3 ) 5 ] À -Liganden gegenüber dem 12-Elektronen [Rh(COD)] + -Fragment aufgrund verringerter elektrostatischer Interaktionen und einer schwächeren π-Donorfähigkeit um � 70 kcal mol À 1 im Vergleich zu [C 5 (CH 3 ) 5 ] À erniedrigt ist. Die quantitative, jedoch reversible Substitution des [C 5 (CF 3 ) 5 ] À -Liganden durch Toluol, die ihn in ein schwach koordinierendes Anion überführt, demonstriert experimentell die außergewöhnlich schwache Bindungssituation.

The incorporation of fluorinated substituents in cyclopentadienyl anions leads to distinct changes in the properties of the corresponding metal complexes, e.g., with regards to electrochemical properties or metal–ligand bonding energies. This review summarizes the synthetic challenges of the preparation and coordination of fluorinated cyclopentadienyl anions.1 Introduction2 Fluorinated Cyclopentadienyls3 Cyclopentadienyls with One CF3 Group4 Cyclopentadienyls with Four CF3 Groups5 Cyclopentadienyls with Five CF3 Groups6 Cyclopentadienyls with ‘Fluorous Ponytails’7 Cyclopentadienyls with C6F5 Groups8 Trends in Interaction Energies9 Conclusion