Tris(thio­cyanato-κN)tris­(triphenyl­phosphine oxide-κO)europium(III)–(nitrato-κ²O,O′)bis­(thio­cyanato-κN)tris­(triphenyl­phosphine oxide-κO)europium(III) (1/1)

The title co-crystal, [Eu(NCS)₃(C₁₈H₁₅OP)₃][Eu(NCS)₂(NO₃)(C₁₈H₁₅OP)₃], contains two distinct neutral complexes. Each complex has threefold symmetry about its central Eu³⁺ ion. As a result, the nitrate-containing mol­ecule contains disorder of its bidentate nitrate and two N-bound thio­cyanate anions, while the [Eu(NCS)₃(OPPh₃)₃] complex is fully ordered. There is a weak π–π stacking inter­action between the phenyl rings of the two mol­ecules [centroid–centroid distance = 4.138 (4) Å].

Tris(thio­cyanato-κN)tris­(triphenyl­phosphine oxide-κO)terbium(III)

The title compound, [Tb(NCS)₃(C₁₈H₁₅OP)₃], contains a six-coordinate Tb^II cation surrounded by three O-bound triphenyl­phosphine oxide ligands and three N-bound thio­cyanate ligands, each in a fac arrangement. There are two crystallographically unique Tb^III atoms in the asymmetric unit. One Tb^III atom resides on a threefold rotation axis, while the other has no imposed crystallographic symmetry. The thio­cyanate ligands are bound through N atoms, illustrating the hard–hard bonding principles of metal complex chemistry.