Synthesis of tripodal tris-phosphonate ligands and the structure of the dimeric complex,[Ce(NO3)3{(EtO)2P(O)CH2)3C6Me3]2

The tris-phosphonates 1,3,5 [(RO)(2)P(O)CH2](3)2,4,6 Me3C6 ( = L-R) have been prepared from the corresponding tribromide and phosphites (RO)(3)P for R = Me, Et, Pr-i and Bu). The phosphonates react with lanthanide nitrates to give dimeric complexes Ln(NO3)(3)L(2)Ln(NO3)(3). The X-ray crystal structure, of the cerium(111) complex is reported. The behaviour of the complexes in solution has been examined by electrospray mass spectrometry and shows that the complex undergoes extensive ligand redistribution, reactions in solution with no evidence for the presence of dimeric species. Molecular modelling calculations show that the tris-chelate monomer is unstable principally due to strain of the aromatic ring. (C) 2003 Elsevier Science Ltd. All rights reserved.