Fluxional behaviour of bis- and tris-(ether phosphine)ruthenium(II) chloro and acetato complexes

Abstract

The syntheses of bis- and tris-[(2-methoxyethyl)diphenylphosphine]ruthenium(II) complexes with chloro, acetato, and trifluoroacetato ligands are described. The complexes are mer-[RuCl₂(P–O)(PO)₂], fac-[RuCl(P–O)₂(PO)]X (X = Cl, SbF₆, or BPh₄), fac-[Ru(P–O)₃][SbF₆]₂, [RuCl(P–O)₂]SbF₆, fac-[Ru(O₂CCH₃)₂(PO)₃], fac-[Ru(O₂CCH₃)(P–O)(PO)₂]X (X = O₂CCH₃ or BPh₄), [RuX₂(O,P)₂](X = O₂CCH₃ or O₂CCF₃), [RuCl(O₂CCH₃)(O,P)₂] and mer-[RuH(O₂CCH₃)(PO)₃]; PO represents the ligand which is co-ordinated via phosphorus only (ether function free), P–O ligand which is co-ordinated in the bidentate chelating mode via phosphorus and oxygen, and O,P is used where the mode of co-ordination is not certain. The mechanism of the fluxional behaviour of these complexes in solution has been investigated by the use of temperature-programmed ³¹P and ¹³C n.m.r. and by nuclear Overhauser enhancement spectroscopy ³¹P n.m.r. studies. Fluxional processes occur through exchange between the bidentate (P- and O-bonded) and the monodentate (P-bonded) co-ordination modes of the ether phosphine ligands, as the labile metal–oxygen bonds are broken and reformed. A second type of fluxional process is observed in the six-co-ordinate tris(ether phosphine) complexes due to Berry-type rearrangements of five-co-ordinate intermediates formed upon opening of a metal–oxygen bond. In several of the complexes both types of fluxional process are operating simultaneously. Other complexes show different types of fluxional behaviour in polar and in non-polar solvents, due to ionic dissociation of chloride and acetate ligands in the polar solvents. Some reactions of the complexes are also discussed.