TiGeS3

The new ternary titanium(II) thiogermanate(IV), TiGeS3, was synthesized using the reactive halide flux method. The title compound shows features of a ribbon-type structure formed from double chains composed of edge-sharing octahedral TiS6 and pyramidal GeS3 units, with all atoms in the asymmmetric unit positioned on mirror planes. While the TiS6 octahedron is regular, the coordination around the Ge atom is rather irregular, which can be described as [3 + 3]. Three S atoms build up a triangle that is bound to the Ge atom, the coordination of which is augmented by three additional S atoms at considerably longer distances. The charge balance can formally be described as [Ti4+][Ge2+][S2−]3.

The new ternary titanium(II) thiogermanate(IV), TiGeS 3 , was synthesized using the reactive halide flux method. The title compound shows features of a ribbon-type structure formed from double chains composed of edge-sharing octahedral TiS 6 and pyramidal GeS 3 units, with all atoms in the asymmmetric unit positioned on mirror planes. While the TiS 6 octahedron is regular, the coordination around the Ge atom is rather irregular, which can be described as [3 + 3]. Three S atoms build up a triangle that is bound to the Ge atom, the coordination of which is augmented by three additional S atoms at considerably longer distances. The charge balance can formally be described as [Ti 4+ ][Ge 2+ ][S 2À ] 3 .

Pilsoo Kim and Hoseop Yun Comment
During an effort to find a new phase in the A-Ti-Ge-S system (A=alkali metals), a new compound was isolated. Here we report the synthesis and structure of the new ternary thiogermanate, TiGeS 3 .
The title compound shows the features of the ribbon-type structure (Fig. 1). Its structure is closely related to that of NH 4 CdCl 3 (Brasseur & Pauling, 1938) and it is isostructural with the previously reported Sn II Sn IV S 3 (Kniep et al., 1982), PbZrS 3 (Lelieveld & Ijdo, 1978), and Sn 1.2 Ti 0.8 S 3 (Gressier et al., 1987). The Ti atom is coordinated by six sulfur atoms in an octahedral arrangement (Fig. 2). The TiS 6 octahedra share an edge to form the one-dimensional chains along the b axis. These chains are fused together sharing two S atoms to form the double chain. These double octahedral chains are capped by the Ge atom to complete the one-dimensional chain.
While the TiS 6 octahedra are regular and the Ti-S distances are in good agreement with those found in other titanium sulfides (Jandali et al., 1980), the coordination around the Ge atom is rather irregular. It can be described as [3 + 3].

Experimental
The title compound, TiGeS 3 was prepared by the reaction of elements with the use of the reactive halide-flux technique. A combination of the pure elements, Ti powder(Aldrich 99.7%), Ge powder(CERAC 99.9%) and S powder(Aldrich 99.999%) were mixed in a fused silica tube in molar ratio of Ti:Ge:S=4:2:7 and then KCl(CERAC 99.9%) was added.
The mass ratio of the reactants and the halide was 1:2. The tube was evacuated to 0.133 Pa, sealed, and heated gradually (20 K/h) to 923 K, where it was kept for 72 h. The tube was cooled to room temperature at the rate 3 K/h. The excess halide was removed with distilled water and black needle-shaped crystals were obtained. The crystals are stable in air and water. A qualitative X-ray fluorescence analysis of the needles indicated the presence of Ti, Ge, and S. The composition of the compound was determined by single-crystal X-ray diffraction.

Refinement
The Ti site in Sn 1.2 Ti 0.8 S 3 has been reported to be occupied by disordered Ti 4+ and Sn 4+ ions (Gressier et al., 1987)

Computing details
Data collection: RAPID-AUTO (Rigaku, 2006); cell refinement: RAPID-AUTO (Rigaku, 2006); data reduction: RAPID-AUTO (Rigaku, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999).  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq