Tetrahedral Networks Containing Beryllium: Syntheses and Structures of Be3(PO4)2 · 2H2O and Be(HAsO4) · H2O

The hydrothermal syntheses and single crystal structures of Be3(PO4)2 · 2H2O and Be(HAsO4) · H2O are described. These phases are built up from vertex-sharing tetrahedra, but their overall structures are quite different. In Be3(PO4)2 · 2H2O, BeO4, BeO2(H2O)2, and PO4 groups build up a three-dimensional structure via Be–O–P and Be–O–Be bonds, resulting in tetrahedral 3- and 4-rings. Be(HAsO4) · H2O is layered and contains 6-rings of BeO3(H2O) and HAsO4 building blocks fused via Be–O–As bonds. Similarities and differences to some other tetrahedral structures are discussed. Crystal data: Be3 (PO4)2 · 2H2O, Mr=253.01, monoclinic, space group C2/c (No. 15), a=15.9640 (6) ?, b=4.5842(2) ?, c=9.5320(4) ?, beta=94.366(2)°, V=695.6(2) ?3, Z=4, R(F)=3.79%, Rw(F)=4.44% [812 reflections with I>2sigma(I)]. Be(HAsO4) · H2O, Mr=166.95, orthorhombic, space group Pca21 (No. 29), a=9.7471(2) ?, b=4.6794(1) ?, c=8.5929(1) ?, V=391.93(9) ?3, Z=4, R(F)=3.93%, Rw(F)=4.32% [795 reflections with I>2sigma(I)].