Crystal chemistry of synthetic Co- and Ni-analogues of natrochalcite; the shortest known hydrogen bonds among mineral-type compounds; Part I, Single-crystal X-ray structures
Crystal chemistry of synthetic Co- and Ni-analogues of natrochalcite; the shortest known hydrogen bonds among mineral-type compounds; Part I, Single-crystal X-ray structures
European Journal of Mineralogy (December 2007) 19 (6): 805-816
- bonding
- cell dimensions
- cobalt
- crystal chemistry
- crystal structure
- hydrogen
- hydrothermal conditions
- infrared spectra
- lattice parameters
- metals
- nickel
- optical spectra
- Raman spectra
- single-crystal method
- spectra
- sulfates
- synthetic materials
- ultraviolet spectra
- unit cell
- X-ray diffraction data
- natrochalcite
Four new representatives of the natrochalcite structure type s.s. - A (super +) Me (sub 2) (super 2+) (X (super 6+) O (sub 4) ) (sub 2) [(H (sub 2) O)(OH)], monoclinic, space group C2/m, Z = 2- with Me (super 2+) = Co or Ni were synthesised under low-hydrothermal conditions and their crystal structures were refined from single-crystal X-ray diffraction data up to sin theta /lambda = 0.904, measured at room temperature and for two compounds also at 105 K. Room temperature data are: NaNi (sub 2) (SO (sub 4) ) (sub 2) [(H (sub 2) O)(OH)]: a = 8.605(1), b = 6.185(1), c = 7.336(1) Aa, beta = 114.78(1) degrees , V = 354.5 Aa (super 3) , R1 = 0.021; NaCo (sub 2) (SO (sub 4) ) (sub 2) [(H (sub 2) O)(OH)]: a = 8.677(1), b = 6.317(1), c = 7.396(1) Aa, beta = 115.40(1) degrees , V = 366.2 Aa (super 3) , R1 = 0.022; NaCo (sub 2) (SeO (sub 4) ) (sub 2) [(H (sub 2) O)(OH)]: a = 8.939(2), b = 6.382(2), c = 7.554(2) Aa, beta = 115.09(1) degrees , V = 390.2 Aa (super 3) , R1 = 0.023; KCo (sub 2) (SeO (sub 4) ) (sub 2) [(H (sub 2) O)(OH)]: a = 9.078(1), b = 6.471(1), c = 7.687(1) Aa, beta = 113.99(1) degrees , V = 412.6 Aa (super 3) , R1 = 0.019. The structure type is built up from chains of edge-sharing MeO (sub 6) octahedra, which are connected by XO (sub 4) tetrahedra and very strong hydrogen bonds to {Me (sub 2) (XO (sub 4) ) (sub 2) [(OH)(H (sub 2) O)]} (super -) sheets. The linkage between these sheets is accomplished by the larger A cations and intermediate to weak hydrogen bonds. Natrochalcite-type compounds are of particular interest due to the occurrence of formal H (sub 3) O (sub 2) (super -) units forming very strong intramolecular hydrogen bonds, e.g. O...O = 2.44 Aa in natrochalcite itself, NaCu (sub 2) (SO (sub 4) ) (sub 2) [(H (sub 2) O)(OH)]. The replacement of Jahn-Teller distorted Cu (super 2+) cations by Co (super 2+) or Ni (super 2+) in the title compounds leads to substantial changes of the MeO (sub 6) coordination polyhedra and, as further consequences, to increased distortions of the XO (sub 4) and AO (sub 8) polyhedra, to the occurrence of short interpolyhedral O...O contacts, and to a further shortening of the strong intramolecular hydrogen bond to O...O = 2.429(2) Aa in NaCo (sub 2) (SO (sub 4) ) (sub 2) [(H (sub 2) O)(OH)] and 2.420(2) Aa in NaNi (sub 2) (SO (sub 4) ) (sub 2) [(H (sub 2) O)(OH)]. These seem to be the shortest hydrogen bond lengths hitherto reported for minerals or mineral-type compounds with fully occupied oxygen donor-acceptor positions. Despite of this fact, the X-ray data corroborate a non-centric, i.e. split position of the hydrogen atom along these short donor-acceptor lines.