Synthesis and Crystal Structure of Ho4S3Si2O7

In an attempt to synthesize the homologous sulfide of KHo2CuSe4 by using KBr as flux in a sealed evacuated quartz tube, transparent crystals of Ho4S3Si2O7 (Mr = 924.08) were isolated. The crystal structure of Ho4S3Si2O7 was determined by single-crystal X-ray diffraction method. Ho4S3Si2O7 crystallizes in a tetragonal system, space group I41/amd (No. 141) with a = 11.666(4), c = 13.593(5) A, V = 1850(2) A3, Z = 8, Dc = 6.64g/cm3, F(000)= 3200, μ(MoKα = 34.79mm-1, final R = 0.0355 and Rw = 0.0378 for 851 reflections with I > 3σ(I). The structure of Ho4S3Si2O7 contains two crystallographically independent Ho3+ cations that are interconnected by S2- anions and the isolated [Si2O7]6- units. Ho(1) is coordinated by three O atoms and three S atoms to form a trigonal prismatic geometry, while Ho(2) is coordinated by six O atoms and three S atoms to form a tricapped trigonal prismatic geometry. The Si2O7 double tetrahedra are in the eclipsed configuration with non-linear Si-O-Si bridges (angle : 129.2(9)°).