ISOMORPHOUS COMPOUNDS [ND(TDTD)1.5(PIC)3] AND [ER(TDTD)1.5(PIC)3] (PIC = PICRATE, TDTD = TRANS-1,4-DITHIANE S,S'-DIOXIDE)

The structures of two isomorphous and isostructural lanthanide derivat ives, ri(picrato-O1,O2)neo-dymium-mu-(trans-1,4-dithione SS-dioxide-S: S')1.5], [Nd(C6H2N3O7)3(C4HgO2S2)1.5], and ly[tri(picrato-01,O2)erbium -mu-(trans-1,4-dithiane SS'-dioxide-S:S')1.5], [Er(C6H2N3O7)3(C4H8O2S2 )1.5], consist of nine-coordinate metal ions, linked to three bidentat e picrate ligands, bound via the phenoxo 0 atom and one 0 atom of an a djacent nitro group, and to three 0 atoms of three TDTD ligands. The T DTD ligands act as bridges that join three neighbouring lanthanide ion s, to give three-dimensional polymers. The coordination polyhedra of t he Nd(III) ana Er(III) ions may best be described as tricapped trigona l prisms.