Trifluorophosphine complexes of rhodium(I): syntheses and ligand-exchange studies

Abstract

The complexes [RhX(CO)2]2(X = Cl, Br, or I) react with an excess of trifluorophosphine at room temperature to afford the red, volatile, crystalline di-µ-halogenotetrakis(trifluorophosphine)dirhodium(I) complexes, [RhX(PF3)2]2, in almost quantitative yield. Binuclear mixed carbonyl trifluorophosphine complexes, Rh2Cl2–(PF3)x(CO)4 –x(x= 1, 2, or 3), are obtained by treatment of [RhCl(CO)2]2 with smaller amounts of PF3, and are also produced as a result of ready intermolecular ligand-exchange reactions between [RhCl(CO)2]2 and [RhCl-(PF3)2]2 in solution at room temperature. The complex [RhCl(PF3)(CO)]2 has one PF3 group co-ordinated to each rhodium atom. The red complexes [RhX(PF3)2]2 react further with PF3 to yield yellow RhX(PF3)4 compounds which are stable at room temperature only under a pressure of PF3. Fluorine-19 n.m.r. studies show that exchange between PF3 or CO and the co-ordinated PF3 ligands of [RhCl(PF3)2]2 occurs easily.