The ligand 4,5-bis(diphenylphosphino)-sym-octahydroacridine N,P,P'-trioxide (10) was obtained from a multistep synthesis and characterized by spectroscopic methods, and two crystal forms were examined by single-crystal X-ray diffraction techniques. The coordination behavior of the trifunctional ligand toward La(NO3)(3) and Nd(NO3)(3) was examined, and the molecular structures of the complexes La(10)(NO3)(3). MeOH and Nd(10)(NO3)(3). MeOH were determined by single-crystal X-ray diffraction methods. The molecules form chains along the z axis in which the ligand bonds in a bidentate mode to one La(NO3)(3) or Nd(NO3)(3) by using the N-O and one of the P=O donor centers. The second P=O donor group in the ligand bridge bonds to a second La(10)(NO3)(3) or Nd(10)(NO3)(3) unit. The coordination behavior of 10 contrasts with that of the related but structurally more flexible trifunctional ligand 2,6-bis[(diphenylphosphino)methyl]pyridine N,P,P'-trioxide, which acts as a tridentate ligand toward f-element ions.