Complexes of lanthanide chlorides with tricyclohexylphosphine oxide. The single crystal X-ray structures and solution properties of pentagonal bipyramidal complexes [Ln(H2O)5(Cy3PO)2]3+·Cy3PO·3Cl− Ln = Dy, Er

Abstract

The products of the reactions of tricyclohexylphosphine oxide, Cy3PO=L, with lanthanide chlorides (Ln=La, Dy, Er, Yb) have been investigated by solution NMR spectroscopy and single crystal X-ray crystallography (Dy, Er). The structures of the complexes are based on a pentagonal bipyramidal arrangement around the central Ln3+ ion with two Cy3PO in axial positions and five water molecules in the equatorial plane with molecular formulae LnLn(H2O)5·L·3Cl·H2O·EtOH. An extensive H-bonding network links the remaining Cy3PO and the chloride ions to the coordinated water molecules to form a polymeric unit. The variable temperature solution 31P NMR spectra in CD2Cl2 and CDCl3 indicate that the solid state and solution structures are similar and that exchange between H-bonded and lanthanide bonded Cy3PO occurs. This exchange is rapid for La but slower for the Er and Yb complexes. Differences in the spectra between the two solvents are discussed in terms of the polarity of the C–D bonds.