Complexes of (EtO)2P(O)CH2P(O)(OEt)2 with lanthanide nitrates

Abstract

The preparation of complexes of (EtO)₂P(O)CH₂P(O)(OEt)₂ = L, with lanthanide nitrates is described. Stable complexes with composition LnL₂(NO₃)₃ can be isolated for Ln = La–Eu and fully characterised. For Ln = Gd–Lu solid compounds could not be isolated. Conductivity and ³¹P NMR spectroscopy indicate structural changes in solution between the lighter and heavier lanthanides and, whilst electrospray mass spectrometry confirms a dramatic difference in behaviour with complexes of the heavier lanthanides readily decomposing via loss of EtNO₃, other experiments show that this does not occur under the conditions of complex formation. The single crystal X-ray structures for Ln = La and Sm show the nitrates and OEt groups to be in close proximity. The changes in spectroscopic properties correlate well with the difficulties in isolating the complexes of heavier metals, and are possibly due to the formation of dimeric complexes rather than loss of ethyl nitrate.