Intramolecular dehydrofluorinative coupling of η6-arene and fluoroarylphosphine ligands in ruthenium complexes

NMR studies of reactions between a series of arene ruthenium(II) fluoroarylphosphine complexes and Proton Sponge have revealed the necessary conditions for intramolecular dehydrofluorinative ligand coupling. The complex must be cationic, and the phosphine need have only one fluoroaryl substituent. The reaction is rapid and clean for [(η6-toluene)RuCl(dfppe)]BF4, [(η6-mesitylene)RuCl{(C6F5)2PC6H4SMe}]BF4 and the diastereomer of [(η6-toluene)RuCl{Ph2PC2H4PPh(C5F4N-4)}]BF4 in which the tetrafluoropyridyl substituent is close to the η6-arene. [(η6-p-cymene)RuCl(dfppe)]BF4 reacts in the presence of Proton Sponge to give a mixture of unidentified compounds. The neutral complex [(η6-toluene)RuCl2{Ph2P(C6F5)}] and the diastereomer of [(η6-toluene)RuCl{Ph2PC2H4PPh(C5F4N-4)}]BF4 in which the tetrafluoropyridyl substituent is distant to the η6-arene do not undergo reaction.