ACTINIDE COMPLEXES OF THE CALIXARENES .2. SYNTHESIS AND CRYSTAL-STRUCTURE OF A NOVEL THORIUM(IV) COMPLEX OF P-TERT-BUTYLCALIX[8]ARENE

The synthesis and room-temperature single-crystal X-ray structure determination of a novel tetranuclear 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 P1BAR, a = 29.51 (2), b = 21.68(3), c = 21.16(1) angstrom, alpha = 60.94(6), beta = 78.75(5), gamma = 87.75(8)-degrees and Z = 2; the structure was refined to a residual of 0.079 for 16 903 'observed' [I > 3-sigma(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 'monodenate' 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 H-1 NMR spectrum has been rationalised in terms of the X-ray structure.