The First Amine‐Templated Layered Metal Selenates

Although a few open‐framework metal sulfates and selenites have been synthesized and characterized recently, it has not been possible to prepare the corresponding selenates, probably because of the instability of the +6 oxidation state of Se in alkaline media. We have been able to synthesize, for the first time, organically templated open‐framework rare earth selenates with the general formula 0.5[C 2 N 2 H 10 ][Ln(H 2 O) 2 (SeO 4 ) 2 ] ( I ) (Ln = La, Nd or Pr) and 0.5[C 4 N 2 H 14 ][La(SeO 4 ) 2 ]·0.5H 2 O ( II ), under hydrothermal conditions in an acidic medium. Crystal data: I (Ln = La): triclinic, space group = P $\bar 1$ , M r = 491.91, a = 7.0105(8) Å, b = 7.3772(9) Å, c = 9.526(1) Å, α = 82.014(2), β = 84.514(2), γ = 84.247(2)°, V = 483.76(1) Å 3 , Z = 2; II : triclinic, space group = P $\bar 1$ , M r = 478.91, a = 5.94(2), b = 7.408(3), c = 11.048(2) Å, α = 86.899(2), β = 75.971(1), γ = 79.456(2)°, V = 463.7(2) Å 3 , Z = 4. Being the first report of complex layered selenates, it is likely to stimulate efforts to synthesize other novel open‐framework structures making use of the selenate ion as the building unit. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)