Diamagnetic Ru(2+) in Na2La2Ti2RuO10-x (0 < x < 2): A Series of Complex Oxides Prepared by Topochemical Reduction

Reaction of the n = 3 Ruddlesden-Popper phase Na2La2Ti2RuO10 with a 5% H2/95% N2 atmosphere between 300 and 900 °C leads to the formation of phases of composition Na2La2Ti2RuO10-x (0 < x < 2) via topochemical reduction. Magnetization data collected from Na2La2Ti2RuO10-x samples in the range 0 < x < 1 show a rapid decline in susceptibility with increasing x, consistent with the conversion of S = 1, Ru(4+) centers at x = 0 to S = 0, Ru(2+) centers at x = 1. We believe this is the first report of diamagnetic Ru(2+) centers in an extended oxide phase. Further reduction of Na2La2Ti2RuO9 leads to the reduction of Ti(4+) to Ti(3+); however, Na2La2Ti2RuO10-x samples in the range 1 < x < 2 exhibit only a very weak paramagnetic response. Given the highly insulating nature of the phases, this suggests the electrons added on reduction of titanium are paired within a local Ti-Ti bonding network in a manner analogous to that observed for TinO2n-1 phases.