Actinide complexes of the calixarenes. Part 2. Synthesis and crystal structure of a novel thorium(IV) complex of p-tert-butylcalix[8]arene

Abstract

The synthesis and room-temperature single-crystal X-ray structure determination of a novel tetra nuclear thorium complex with p-tert-butylcalix[8]arene, H₈L, has been achieved, the stoichiometry being assigned as [Th₄(HL)(H₂L)(dmso)₄(OH)₃(OH₂)]·dmso·2H₂O (dmso = Me₂So). Crystals of the complex are triclinic, space group P, a= 29.51(2), b= 21.68(3), c= 21.16(1)Å, α= 60.94(6), β= 78.75(5), γ= 87.75(8)° and Z= 2; the structure was refined to a residual of 0.079 for 16 903 ‘observed’[I > 3σ(I)] reflections. Each calixarene unit, one with approximate 2 and the other approximate mm symmetry, is co-ordinated to two thorium atoms, the environment of each thorium comprising five ligand phenolic oxygen atoms, three being ‘monodentate’ and two bridging, with a monodentate O-bonded dmso entering through each cup of each ligand, and hydroxide groups variously bridging to the other thorium within the same ligand, and binding the two Th₂L systems together. The ¹H NMR spectrum has been rationalised in terms of the X-ray structure.