The crystal structures of two lanthanide phosphites and the geometry of metal phosphite complexes
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As part of a continuing study on the synthesis and structure of metal phosphites, two compounds, Ce(HO3PH)(O3PH)·2H2O and La(HO3PH)(O3PH)·3H2O were prepared and their crystal structures determined by X-ray single crystal methods. The cerium compound crystallizes in the orthorhombic space group P212121 with a=7.126(4), b=16.539(4), c=6.762(1) Å and Z=4. The compound is a layered one with layers centered at 1 4 and 3 4b. Each Ce is eight coordinate in a distorted dodecahedral geometry. One phosphite group chelates the metal and the chelating oxygens also bond to adjacent cerium atoms forming a chain. The other oxygen of this group bridges cerium atoms in a direction roughly perpendicular to the chain formed by the chelating oxygens to bind the chains into layers. The other phosphite group bridges adjacent cerium atoms along the same direction as the chelating atoms bridge and is alternately above and below the layer. The eighth coordination site is occupied by a water molecule. Another water molecule resides between the layers creating a hydrogen bond network which binds the layers together. The lanthanum compound is monoclinic, P21/c with a=9.680(2), b=7.135(1), c=13.479(2) Å, β=104.54(2)°, V=901.0(3) Å3 and Z=4. The layer structure is very similar to that for the cerium phosphite but two water molecules reside between the layers binding them together through an extensive hydrogen-bond network. These structures are discussed in the light of previous work on phosphites and phosphonates. © 1992.
author list (cited authors)
Zhang, Y., Hu, H., & Clearfield, A.