Tetra-μ3-tert-butanolato-tetrathallium(I)

The title compound, [Tl4(C4H9O)4], featuring a (Tl—O)4 cube, crystallizes with a quarter-molecule (located on a special position of site symmetry ..) and a half-molecule (located on a special position of site symmetry 23.) in the asymmetric unit. The Tl—O bond distances range from 2.463 (12) to 2.506 (12) Å. All O—Tl—O bond angles are smaller than 90° whereas the Tl—O—Tl angles are wider than a rectangular angle.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: KJ2165).
References Blessing, R. H. (1995). Acta Cryst. A51, 33-38. Flack, H. D. (1983) 2008;Lerner et al. 2005Lerner et al. , 2002. In most cases the reactions that occur between alkali metal alkoxides and transition metal halides are not quantitative. Another approach to complexes with chalcogen coordination is to start from thallium alkoxides which react almost quantitatively with transition metal chlorides due to the poor solubility of TlCl. In this paper we report the synthesis and the crystal structure of [TlOtBu] 4 . The title compound [TlOtBu] 4 was prepared according to a slightly changed published procedure (Schmidbaur et al. 1968), as shown in Fig. 2. The following modifications have been made in our approach: thallium ethoxide was used instead of thallium methoxide and potassium tert-butoxide was substituted for sodium tert-butoxide.

Experimental
In a flame-dried vial 1.1 ml thallium ethoxide (3.77 g, 15.1 mmol) was added to 1.70 g potassium tert-butoxide (15.1 mmol) in 50 ml benzene. After flame-sealing, the vial was heated to 80 °C for four days. The vial was opened, the crude reaction mixture filtered hot under an nitrogen atmosphere, the solid residue was washed with 20 ml benzene and the combined filtrates evaporated to dryness. The remaining colorless solid was suspended in ether and allowed to settle. A sample of the supernatant was transferred to a flame-dried Schlenk vessel and stored at -35°C. After two days colorless crystals of the composition [TlOtBu] 4 deposited and were separated from the mother liquor (Yield 15%).

Refinement
H atoms were located in a difference map, but geometrically positioned and refined using a riding model with fixed individual displacement parameters [U(H) = 1.5 U eq (C)] and with C-H = 0.98 Å.
supplementary materials sup-2 Figures   Fig. 1. Perspective view of one of the two independent molecules of the title compound with the atom numbering scheme for the symmetry independent atoms; displacement ellipsoids are at the 50% probability level; H atoms are omitted for clarity.

Tetra-µ 3 -tert-butanolato-tetrathallium(I)
Crystal data [Tl 4  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 Rfactors(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.