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-dione (diphenylaminosquarate) with
metal salts of La, Eu, Gd and Tb produced the first set of lanthanide complexes with a monosubstituted
aminosquarate ligand. The lanthanum complex La[(C6H5)2NC4O3]3(H2O)6·5H2O (1) is monomeric and crystallizes
in the triclinic space group P1̄, with a nine-coordinate La center bonded to three pendant diphenylaminosquarate
groups and six aqua ligands. The Eu, Gd, and Tb complexes [M(μ-(C6H5)2NC4O3)((C6H5)2NC4O3)(NO3)(OH2)4]2·4H2O (2−4) are isomorphous (also P1̄), each metal atom being nine-coordinate and bridged to its neighbor by
two diphenylaminosquarate ligands in a μ-1,2- fashion; the coordination polyhedron around each metal is completed
by a pendant diphenylaminosquarate ligand, four aqua ligands, and a chelating nitrate ion. The resistance of the
diphenylamino substituent to hydrolysis, vis-à-vis the hydrolysis of dialkylamino substituents, is discussed.

配位化合物3-二苯氨基-4-羟基环丁-3-烯-1,2-二酮（二苯氨基 squarate）与镧、铕、钆和铽金属盐的复合作用，产生了第一组以单取代氨基 squarate 配体为特征的镧系金属复合物。镧复合物La[(C6H5)2NC4O3]3(H2O)6·5H2O（1）为单分子结构，并以三斜晶系P1̄空间群结晶，其中心镧原子以九配位与三个悬挂的二苯氨基 squarate 群和六个水合配体相连。铕、钆和铽复合物[M(μ-(C6H5)2NC4O3)((C6H5)2NC4O3)(NO3)(OH2)4]2·4H2O（2−4）为同构（亦为P1̄），每个金属原子均为九配位，并通过两个二苯氨基 squarate 配体以μ-1,2-形式与其相邻原子桥接；每个金属原子周围的配位多面体由一个悬挂的二苯氨基 squarate 配体、四个水合配体和一个螯合硝酸根离子完成。对于二苯氨基取代基相对于二烷基氨基取代基在抗水解性方面的讨论。