Introducing the Perfluorinated Cp Ligand into Coordination Chemistry

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

Automated summary

This study successfully synthesized the fluorocarbon-soluble complex [Rh(COD)(C-5(CF3)(5))] through salt metathesis, demonstrating for the first time the coordination ability of the weakly basic [C-5(CF3)(5)](-) ligand. The byproduct [Rh(COD)(C-5(CF3)(4)H)] was also isolated and characterized. DFT studies showed that the interaction energy between the [C-5(CF3)(5)](-) ligand and the 12-electron fragment [Rh(COD)](+) is significantly lower compared to [C-5(CH3)(5)](-), indicating reduced electrostatic interactions and weaker pi-donor properties of the [C-5(CF3)(5)](-) ligand.