Arene carbonyl rhodium(I) complexes

Abstract

The arene carbonyl rhodium complexes, [Rh(C6Me6)(CO)2]PF6 and [Rh(C6Me6)(CO)PPh3]PF6, have been prepared by treating the dimeric complexes, [RhCl(CO)2]2 and [RhCl(CO)PPh3]2, with AgPF6 in the presence of hexamethylbenzene. The reaction of [Rh(C6Me6)(CO)2]PF6 with tetrafluorobenzobarrelene affords [Rh(C6Me6)(TFB)]PF6. On the other hand, the reaction of [Rh(arene)(CO)2]PF6 with a stoichiometric amount of triphenylphosphine gives [Rh(arene)(CO)PPh3]PF6 (arene = C6Me6 or C6H3Me3), whereas with excess of this ligand [Rh(CO)(PPh3)3]PF6 is formed. The related [Rh(C6Me6)(CO)P(p-MeC6H4)3]PF6 derivative has also been prepared.The reactivity of both hexamethylbenzene carbonyl rhodium complexes has been examined. The addition of bipyridine to solutions of [Rh(C6Me6)(CO)L]PF6 (L = CO or PPh3) causes the immediate displacement of the coordinated hexamethylbenzene. Their reactions with the nucleophiles, acetylacetonate, tropolonate, or pyrazolate in the presence of triethylamine afford neutral derivatives of the type [RhA(CO)L]x (L = CO or PPh3; A = acac or trop, x = 1; A = pz, x = 2).