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

The crystal structure of a novel Ni-containing precursor to the molecular s ieve AlPO4-34 (CHA framework type) has been determined in its as-synthesize d 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 th e triclinic unit cell Of C4H18N4NiAl6P6O26 (a = 9.0854(9) Angstrom, b = 9.3 327(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 conne ctivity of the aluminophosphate framework is related to that of AlPO4-34, i t is not identical because some P-O-Al bridges are broken. The Al atoms ass ociated with this disruption of the connectivity form double Al-O-Al bridge s 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 c age. The triclinic deformation associated with these structural features di sappears upon calcination, when the Ni(II) complex decomposes and the fully connected CHA framework type forms. (C) 2001 Elsevier Science B.V. All rig hts reserved.