SrFe0.5Ru0.5O2: square-planar Ru2+ in an extended oxide.

Low-temperature topochemical reduction of the cation disordered perovskite phase SrFe(0.5)Ru(0.5)O(3) with CaH(2) yields the infinite layer phase SrFe(0.5)Ru(0.5)O(2). Thermogravimetric and X-ray absorption data confirm the transition metal oxidation states as SrFe(0.5)(2+)Ru(0.5)(2+)O(2); thus, the title phase is the first reported observation of Ru(2+) centers in an extended oxide phase. DFT calculations reveal that, while the square-planar Fe(2+) centers adopt a high-spin S = 2 electronic configuration, the square-planar Ru(2+) cations have an intermediate S = 1 configuration. This combination of S = 2, Fe(2+) and S = 1, Ru(2+) is consistent with the observed spin-glass magnetic behavior of SrFe(0.5)Ru(0.5)O(2).