Introducing the Perfluorinated Cp* Ligand into Coordination Chemistry.

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.