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, Rh₂Cl_2^–(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.