Hydrothermal Synthesis and Structural Characterization of Two Layered Diamine Pentamolybdates: (C2H10N2)[Mo5O16] and (C4H12N2)[Mo5O16]

The two diamine pentamolybdates, (C2H10N2)[Mo5O16] and (C4H12N2)[Mo5O16], have been hydrothermally synthesized (180°C, 24 h, autogenous pressure). The ethylenediamine pentamolybdate was powdered and its structure was solved ab initio from conventional X-ray powder diffraction. Single crystals of piperazine pentamolybdate could be isolated. Despite a similar topology, the structures crystallize in different unit cells: ethylenediamine pentamolybdate crystallizes in the monoclinic system with a=15.801(1) ?, b=5.5878(4) ?, c=9.3743(7) ?, and beta=116.321(6)°, space group is P2/n with Z=2; piperazine compound is also monoclinic, space group C2/c with a=23.3997(3) ?, b=5.6222(1) ?, c=14.4131(2) ?, beta= 115.960(1)° and Z=4. Both structures are built from [Mo5O16]2- layers composed of stripes of ReO3-type, as already found in Cs2Mo5O16. Diamine cations are located between the layers and ensure the connectivity of the structure via hydrogen bonds. The relationship between the two structures is discussed.