Crystal structure of new hexahydrate dicobalt pyrophosphate Co2P2O7·6H2O: comparison with Co2P2O72H2O, α-, β- and γ-Co2P2O7

Abstract A new dicobalt pyrophosphate, Co2P2O7·6H2O, has been synthesized and characterized by single crystal X-ray diffraction. The compound belongs to the mono clinic space group P21/n, and its unit cell dimensions are: a = 7.2077(2), b = 18.3373(5), c = 7.6762(2) Å, β = 92.4356(15)°, V = 1013.64(5) Å3, Z = 4. The structural parameters were refined to an R index of 0.0570 for 1937 reflections with I>2σ(Io). The framework of this pyro phosphate is made by the packing of layers of discrete CoO6 octahedra connected by double tetrahedra P2O7 groups. The (P2O7)4– anion group shows bent eclipsed conformation. A comparative study among anhydrous (α-, β- and γ-Co2P2O7) and hydrated forms (Co2P2O7·2H2O) of dicobalt pyrophosphates known in literature is presented.

[1]  M. Bolte,et al.  Rerefinement of cobalt diphosphate against new intensity data , 2002 .

[2]  M. Morcrette,et al.  Crystal structure of a new vanadium(IV) diphosphate: VP2O7, prepared by lithium extraction from LiVP2O7 , 2001 .

[3]  J. Christoffersen,et al.  Structure of the β form of calcium pyrophosphate tetrahydrate , 2000 .

[4]  H. Fjellvåg,et al.  Synthesis and crystal structure of the hydrated magnesium diphosphate Mg2P2O7·3.5H2O and its high temperature variant Mg2P2O7·H2O , 2000 .

[5]  Maria Cristina Burla,et al.  SIR97: a new tool for crystal structure determination and refinement , 1999 .

[6]  Louis J. Farrugia,et al.  ORTEP-3 for Windows - a version of ORTEP-III with a Graphical User Interface (GUI) , 1997 .

[7]  E. M. Holt,et al.  σ-Dibarium Pyrophosphate. , 1995 .

[8]  R. Blessing,et al.  An empirical correction for absorption anisotropy. , 1995, Acta crystallographica. Section A, Foundations of crystallography.

[9]  L. Novakovíc,et al.  Structural phase transitions in Co(II) and Ni(II) diphosphates in the temperature range 290–1000 K , 1994 .

[10]  H. Effenberger,et al.  Comparison of the Crystal Structures of Co2(X2O7)×2 H2O, X: P and As. , 1993 .

[11]  C. Lecomte,et al.  Crystal chemistry of Mg2P2O7.nH2O, n = 0, 2 and 6: magnesium-oxygen coordination and pyrophosphate ligation and conformation. , 1992, Acta crystallographica. Section B, Structural science.

[12]  M. Wildner.  On the geometry of Co(II)O6 polyhedra in inorganic compounds , 1992 .

[13]  M. Wildner.  On the geometry of Co(II)O6polyhedra in inorganic compounds , 1992 .

[14]  B. Sales,et al.  Structure of dichromate-type lead pyrophosphate, Pb2P2O7 , 1986 .

[15]  A. Nord,et al.  Structure studies of thortveitite‐like dimanganese diphosphate, Mn2P2O7 , 1984 .

[16]  A. Nord,et al.  Structural studies of thortveitite-like Mn2P2O7 , 1984 .

[17]  J. S. Swinnea,et al.  Crystal structure of Fe2P2O7 , 1983 .

[18]  A. Kawahara,et al.  The structure of synthetic dimagnesium diphosphate(V) dihydrate , 1982 .

[19]  N. Mandel,et al.  The crystal structure of calcium pyrophosphate dihydrate , 1975 .

[20]  D. Corbridge.  The structural chemistry of phosphorus , 1974 .

[21]  S. Schneider,et al.  Crystal structure of manganese pyrophosphate dihydrate Mn2P2O7.2H2O , 1973 .

[22]  N. Krishnamachari,et al.  The crystal structure of cobalt diphosphate , 1972 .

[23]  B. E. Robertson,et al.  Crystal structure of αZn2P2O7 , 1970 .

[24]  C. Calvo,et al.  Crystal structure of Cd2P2O7 , 1969 .

[25]  J. Paasiv́irta,et al.  The Crystal Structure of alpha-Sr2P2O7. , 1968 .

[26]  C. Calvo.  The crystal structure of α‐Mg2P2O7 , 1967 .

[27]  B. E. Robertson,et al.  The crystal structure and phase transformation of α-Cu2P2O7 , 1967 .

[28]  N. C. Webb.  The crystal structure of -Ca2P2O , 1966 .

[29]  D. Cruickshank,et al.  A reinvestigation of the crystal structure of thortveitite Sc2Si2O7 , 1962 .