The complexing properties of the phenylsquarate ligand with Ru(II), Pt(II), Gd(III) and Tb(III) ions

Reaction of 3-phenyl-4-hydroxycyclobut-3-ene-1,2-dione (phenylsquarate) wit h Ru(dmso)(4)Cl-2 in acetonitrile afforded crystals of the monomeric specie s Ru(dmso)(3)Cl(H2O)(C6H5C4O3).H2O (1) in which the ruthenium is in a sligh tly distorted octahedral geometry with three fac S-bonded dmso ligands. No complexation occurs when Pt(NH3)(4)Cl-2 is reacted with the same ligand in aqueous solution: instead, the hydrogen-bonded salt [Pt(NH3)(4)][C6H5C4O3]( 2).H2O (2) is produced. The isomorphous complexes {[M(mu -C6H5C4O3)(C6H5C4O 3)(2)(H2O)(4)].H2O}(n) [M = Tb (3), Gd (4)] formed by the reaction of the p henylsquarate ligand with the respective metal nitrate contain eight-coordi nate metal centres surrounded by two mu -1,3-bridged and two pendant phenyl squarate ligands and four aqua ligands, Tn the solid state, 3 and 4 form in terleaved pi -stacked and hydrogen-bonded sheets with pronounced hydrophobi c and hydrophilic surfaces, In compounds 1-4, the phenylsquarate ligands pa rticipate in pi-pi interactions and exhibit multiple bond localisation, the pattern of bonding being the same in each structure. (C) 2001 Elsevier Sci ence B.V. All rights reserved.