Abstract
The reaction of AgBF(4) and [Rh(COD)Cl](2) (COD=1,5-cyclooctadiene) in presence of [NEt(4) ][C(5) (CF(3) )(5) ] afforded the fluorocarbon soluble complex [Rh(COD)(C(5) (CF(3) )(5) )] by salt metathesis. This complex represents the first example for a successful coordination of the weakly basic [C(5) (CF(3) )(5) ](-) ligand, since its first synthesis in 1980. In addition to [Rh(COD)(C(5) (CF(3) )(5) )] also the byproduct [Rh(COD)(C(5) (CF(3) )(4) H)] was isolated and fully characterized. Accompanying DFT studies showed that the interaction energy of the [C(5) (CF(3) )(5) ](-) ligand towards the 12-electron fragment [Rh(COD)](+) is ≈70 kcal mol(-1) lower in comparison to [C(5) (CH(3) )(5) ](-) due to reduced electrostatic interactions and weaker π-donor properties of the ligand. The quantitative but reversible substitution of the [C(5) (CF(3) )(5) ](-) ligand by toluene, converting it into a weakly coordinating anion, experimentally proved the extraordinary weak bonding interaction.