Six-fold Oxygen-Coordinated Triplet (<i>S</i> = 1) Palladium(II) Moieties Templated by Tris(bipyridine)ruthenium(II) Ions

Tris(bipyridine)ruthenium(II) is used as a templating agent to insert palladium(II) into three-dimensional oxalate-based networks. The templated-assembly of [Ru(bpy)3][Pd2(ox)3] (Pd2) and [Ru(bpy)3][PdMn(ox)3] (PdMn) is described. The latter compound is structurally characterized by powder X-ray diffraction and X-ray absorption spectroscopy. These techniques reveal an unusual 6-fold oxygen environment around the Pd(II) atoms with two short (2.02 Å) and four long (2.17 Å) Pd−O distances. As stated by magnetometry, this environment is associated with a triplet ground state (S = 1) of the palladium(II) ion: when the temperature is decreased, the χMT product shows a monotonous decrease from 5.54 cm3 K mol-1 at 300 K, a value which is slightly lower than the one expected for independent paramagnetic Pd(II) (S = 1, g = 2) and Mn(II) (S = 5/2, g = 2) ions. This thermal variation is due to antiferromagnetic exchange interactions between the two spin bearers. Nevertheless, no long-range magnetic order is detected down to 2 K. These results are confirmed by an analysis of the [MII(C2O4)3]4- (M = Ni, Pd, Pt) complex and of a [PdII{μ-(C2O4)MnII(OH2)4}3]2+ tetranuclear model using density functional theory.