HYDROTHERMAL SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF TWO LAYERED DIAMINE PENTAMOLYBDATES: (C2H10N2)[Mo5O16] AND (C4H12N2)[Mo5O16]

摘要

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 powder XRD. 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) angstroms, b=5.5878(4) angstroms, c=9.3743(7) angstroms, and beta=116.321(6) degrees, space group is P2 with Z=2; piperazine compound is also monoclinic, space group C2/c with a=23.3997(3) angstroms, b=5.6222(1) angstroms, c=14.4131(2) angstroms, beta=115.960(1) degrees 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 H bonds. The relationship between the two structures is discussed. 25 refs.