Introducing the Perfluorinated Cp* Ligand into Coordination Chemistry

Abstract

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.