Magnetic properties by unusual coordination and oxidation states
In this project magnetically interesting phenomena are induced via unusual coordination spheres or the creation of unusual oxidation states. An example of an unsual metal coordination is the octahedral surrounding of the Pd2+ ions in the disulfate Pd(S2O7) (Fig. 1, left), which we were able to synthesize via the reaction of elemental Palladium with SO3. In spite of the electronic d8 configuration nearly undistorted octahedral coordination of oxygen atoms is very uncommon and has never been observed for simple coordination compounds before. This unusual surrounding of the Pd2+ ions leads to paramagnetism of the compound and to ferromagnetic ordering of at low temperatures (11.6 K) which has never been observed before for a Pd(II) compound.
Fig. 1 Octahedral Pd2+ coordination in the crystal structure of Pd(S2O7) (left) and the magnetic properties of the compound (right).
Unusual oxidations states are possible via special synthetic routes, even under alleged oxidative reaction conditions. An older example is the Gold(II)sulfate Au2(SO4)2 with a dumbbell shaped Au22+ ion, which could be prepared via the reaction of Au(OH)3 in conc. H2SO4, a more recent example is the stabilization of Mo(V) in the unusual sulfate-hydrogensulfate MoO(SO4)(HSO4) (Fig. 2), which could be obtained via the reaction of Mo(CO)6 in Oleum. Also for the element Vanadium a number of low and mixed valent sulfates could be synthesized and characterized with the help of magnetic measurements.
Fig. 2 Crystals of MoO(SO4)(HSO4)