New Open-Framework Ammonium and Amine Cadmium Zirconium Oxalates with Helical Structures

Abstract

Two new open-framework cadmium zirconium oxalates containing ammonium or ethylenediamine have been prepared from precipitation methods at room pressure. The crystal data of these oxalates are as follows:The two structures are built from MO 8 (M ) Cd, Zr) distorted antiprisms connected by oxalate groups to give rise to chains based on the sequence ...-Cd-oxalate-Zr-oxalate-... that display a helical wire arrangement. Each helix is connected to six neighboring ones to form an anionic three-dimensional framework [CdZr(C 2 O 4 ) 4 ] 2-balanced by the cations NH 4 + or [NH 3 -(CH 2 ) 2 -NH 3 ] 2+ located in tunnels parallel to the c axis that also contain water molecules. The apertures have hexagonal and square cross sections of ∼5.7 Å and ellipsoidal cross sections of 5.7 × 12 Å. There is extensive hydrogen bonding among the ammonium and amine groups, water molecules, and framework. The thermal decomposition of the two compounds into cadmium and zirconium oxides is described.

X-ray diffraction, 133Cs and 1H NMR and thermal studies of CdZrCs1.5(H3O)0.5(C2O4)4·xH2O displaying Cs and water dynamic behavior

“…Even though the structure framework topology of this new cesium phase is analogous to that of previously reported compounds CdZrA(C 2 O 4 ) 4 ·x H 2 O [A ¼ Na 2 , (NH 4 ) 2 , (C 2 N 2 H 10 )] [3,4], the title compound possesses interesting features. One of these concerns its nonstoichiometry in cesium which is to be associated with cationic exchange properties.…”

“…This structure has been reported for three compounds with inserted (metallic and organic) cations of different charges, i.e. CdZr(NH 4 ) 2 (C 2 O 4 ) 4 ·3.9-H 2 O [3], CdZr(C 2 N 2 H 10 )(C 2 O 4 ) 4 ·4.4H 2 O [3] and CdZrNa 2 (C 2 O 4 ) 4 ·8.5H 2 O [4]. For the last material, a dynamic disorder of the cations and water molecules located inside the channels was pointed out from singlecrystal X-ray diffraction and 1 H and 23 Na solid-state NMR.…”

“…The parameters of an helix, as defined in Ref. [3], are its period P ¼ c ¼ 23; 656 Å and its radius r ¼ a=2 ¼ 4:553 Å . The total volume available for the disordered cesium and hydronium cations is 802 Å 3 , which corresponds to approximately 47% of the unit-cell volume.…”

“…Two open structure frameworks have been pointed out in the family [2,3]. Both of them are built from [CdZr(C 2 O 4 ) 4 ] 22 anionic groups forming two different frameworks with a topology originating from the two frequent configurations in the stereochemistry of eight-fold coordination, i.e.…”

Network analysis of barium oxalates Ba(C2O4)m(HC2O4)n(H2C2O4)p(H2O)q, including the new, uniform, five-connected loh net

“…The corresponding eight-coordinated [M(C 2 O 4 ) 4 ] nÀ building blocks require larger metal ions such as the heavier d 10 or d 0 ions. An example of the 6 4 .8 2 -qtz net is found in CdZr(C 2 O 4 ) 4 (NH 4 ) 2 Á3.9H 2 O and in the related CdZr(C 2 O 4 ) 4 (H 3 NCH 2 CH 2 NH 3 ) 2 Á4.4H 2 O, [25] and other analogous compounds have been reported [26][27][28][29]. The [M(C 2 O 4 ) 4 ] nÀ unit also provides one node in the unusual eightand four-connected (4 4 .6 2 ) 2 (4 16 .6 12 )-scu net found in [Ca[Co(en)-(C 2 O 4 ) 2 ] 2 ] n [30].…”