A variety of new tri- and tetranuclear Mn–Ln and Fe–Ln (Ln = lanthanide) complexes

The use of carboxylates in the synthesis of 3d/4f clusters, with or without a second organic ligand, has afforded a series of tetranuclear M2Gd2 complexes (M = Fe or Mn), and two new trinuclear M2Gd (M = Fe or Mn) molecular compounds. Only one of these, [Mn2Gd2O2(O2CBut)8(HO2CBut)4] (1), does not contain a multidentate chelate ligand. Two other similar tetranuclear clusters were synthesized from the use of triethanolamine (teaH3) and 1,1,1-tris(hydroxymethyl)ethane (thmeH3). [Mn2Gd2(OH)2(O2CPh)4(NO3)2(teaH)2] (2) has very similar structure with 1, bearing a defective incomplete double-cubane core bridged by μ3-O atoms, whereas in the core of [NHEt3]2[Fe2Gd2(O2CPh)4(thme)2(NO3)4] (3) the thme3− ligand caps the two incomplete cubane units, providing the triply-bridging alkoxides needed for bridging. Two new oxide-centered triangular clusters were synthesized bearing the Schiff-based chelate 2-{[2-(dimethylamino)ethyl]methylamino}ethanol (dmemH), namely [Fe2GdO(O2CBut)2(dmem)2(NO3)3] (4), and [Mn2GdO(O2CBut)2(dmem)2(NO3)3] (5). Magnetic susceptibility measurements and/or reduced magnetization studies established that complexes 1 and 3 have an S = 5 ground state, complex 2 has S = 4, and complexes 4 and 5 are S = 7/2 in their ground states. These complexes portray the feasibility of obtaining products bearing metal cores commonly found in homometallic clusters, even when these include metals with completely different coordination chemistry and electronic structure, such as lanthanides.

Three tetranuclear diamond-shaped M2Gd2, and two trinuclear M2Gd oxide-centered triangles (M = FeIII or MnIII) have been synthesized and characterized. These complexes represent proof of feasibility for the isolation of mixed 3d/4f clusters with structural features commonly found in homometallic transition metal cluster chemistry.Figure optionsDownload as PowerPoint slide