Rietveld refinement of a chabazite-like aluminophosphate containing a [Ni(1,2-diaminoethane)(2)O-2](2-) complex bridge

Abstract

The crystal structure of a novel Ni-containing precursor to the molecular sieve AlPO4-34 (CHA framework type) has been determined in its as-synthesized form using high-resolution synchrotron powder diffraction data. One [Ni(1,2-diaminoethane)(2)O-2](2-) complex is found per chabazite-like cage in the triclinic unit cell Of C4H18N4NiAl6P6O26 (a = 9.0854(9) Angstrom, b = 9.3327(3) Angstrom, c = 8,936(1) Angstrom, alpha = 86.27(6)degrees, beta = 101.26(6)degrees, gamma = 92.72(5)degrees, P (1) over bar). Although the connectivity of the aluminophosphate framework is related to that of AlPO4-34, it is not identical because some P-O-Al bridges are broken. The Al atoms associated with this disruption of the connectivity form double Al-O-Al bridges and are five-coordinate, while the P atoms interact strongly with the Ni(II) complex ion to form an unusual P-O-Ni-O-P bridge across the chabazite cage. The triclinic deformation associated with these structural features disappears upon calcination, when the Ni(II) complex decomposes and the fully connected CHA framework type forms.