Lanthanide complexes of 3-diphenylamino-4-hydroxycyclobut-3-ene-1,2-dione(diphenylaminosquarate)

Complexation of the ligand 3-diphenylamino-4-hydroxycyclobut-3-ene-1,2-dion e (diphenylaminosquarate) with metal salts of La, Eu, Gd and Tb produced th e first set of lanthanide complexes with a monosubstituted aminosquarate li gand. The lanthanum complex La[(C6H5)(2)NC4O3](3)(H2O)(6). 5H(2)O (1) is mo nomeric and crystallizes in the triclinic space group P (1) over bar, with a nine-coordinate La center bonded to three pendant diphenylaminosquarate g roups and six aqua ligands. The Eu, Gd, and Tb complexes [M(mu-(C6H5)(2)NC4 O3)((C6H5)(2)NC4O3)(NO3)(OH2)(4)](2). 4H(2)O (2-4) are isomorphous (also P (1) over bar), each metal atom being nine-coordinate and bridged to its nei ghbor by two diphenylaminosquarate ligands in a mu-1,2-fashion; the coordin ation polyhedron around each metal is completed by a pendant diphenylaminos quarate ligand, four aqua ligands, and a chelating nitrate ion. The resista nce of the diphenylamino substituent to hydrolysis, vis-a-vis the hydrolysi s of dialkylamino substituents, is discussed.