Assembly of 3‐D Network Structures Containing Oxydiacetate and CeIII or CeIV

Abstract

AbstractReaction of CeCl3·7H2O with Na2(oda) (oda = O(CH2CO2)22— oxydiacetate) in a 2:3 ratio gives the neutral cerium(III) complex [Ce2(oda)3(H2O)3]·9H2O (1). Treatment of a 1:3 mixture of CeCl3·7H2O and H2oda in water with 4 molar equivalents of NaOH also gives 1 but, with a larger excess of NaOH, the tri‐sodium salt Na3[Ce(oda)3]·9H2O (2) is isolated. Formation of a tri‐ammonium analogue of 2 can be achieved by neutralisation of an aqueous solution of CeCl3·7H2O and H2(oda) in a 1:3 ratio by NH4OH, giving (NH4)3[Ce(oda)3]·7H2O (3). Use of the cerium(IV) reagent (NH4)2[Ce(NO3)6] with Na2(oda) results in reduction to cerium(III) under ambient conditions and isolation of 1. However, in the absence of light this reaction yields crystals of the novel cerium(IV) heterobimetallic [Ce(oda)3Na4(NO3)2] (4). Each of these complexes exhibit a 3‐D network structure having a common nine‐coordinate [Ce(oda)3]n— (n = 2 or 3) subunit, irrespective of the oxidation state of cerium. In 1, six [Ce(oda)3]3— anions are connected, through bridging bidentate carboxylates, to a second Ce3+ site further coordinated by three water molecules. In contrast, the ammonium salt 2, displays isolated [Ce(oda)3]3— anions, devoid of further carboxylate bonding, but enmeshed within a network of hydrogen‐bonded NH4+ cations and water molecules. The remarkable structure of 4 consists of infinite 2‐D sheets of [Na2(NO3)]+ pillared by [Ce(oda)3]2— units, the connectivity arising by multidentate nitrate and carboxylate bridging.