Platinum group metal complexes of a bis(diphenylphosphino)ethane ligand containing perfluoroalkyl ponytails

Abstract

The perfluoroalkyl-derivatised bidentate phosphine (4-F₁₃C₆C₆H₄)₂PCH₂CH₂P(C₆H₄C₆F₁₃-4)₂ reacted with [PtCl₂(MeCN)₂], [PdCl₂(MeCN)₂] or [{RhCl(COD)}₂] to yield the complexes [PtCl₂(L–L)] 1, [PdCl₂(L–L)] 2 and [Pd(L–L)₂]²⁺2Cl^– 3 or [{RhCl(L–L)}₂] 5 respectively. Complex 3 was reduced with NaBH₄ to [Pd(L–L)₂] 4 and the chloride bridges in 5 were cleaved with triphenylphosphine to yield [RhCl(L–L)(PPh₃)] 6. The reaction of the ligand with [{RhCl₂(η⁵-C₅Me₅)}₂] in a 1∶1 or a 2∶1 ratio yielded either [{RhCl₂(η⁵-C₅Me₅)}₂(L–L)] 7 or, after metathesis with NH₄BF₄ in acetone, [RhCl(η⁵-C₅Me₅)(L–L)]⁺BF₄^– 8 respectively. Throughout, spectroscopic studies indicated that the ligand co-ordinates in a similar fashion to bis(diphenylphosphino)ethane (dppe). Complex 7 and the analogous dppe complex are fluxional at room temperature. At the low temperature limit, all the nuclei within these molecules are chemically inequivalent for which simulation suggests a gauche-eclipsed conformation around the PCH₂–CH₂P bond. Solubility studies indicated that only 4 and 5 are preferentially soluble in perfluorocarbon solvents.