Crystal structure of trimethylthallium

The crystal structure of Me3TI has been determined by single-crystal X-ray diffraction. The crystals are tetragonal, space group P42/n, with Z= 8 in a unit cell of dimensions a=b= 13·464 ± 0·010, c= 6·379 ± 0·009 Å. The structure may be regarded as a polymeric three-dimensional framework constructed of asymmetric but approximately linear TI–Me ⋯ TI units, with one non-bridging methyl group attached to each thallium atom. The compound is formally isostructural with trimethylindium; both structures may be considered to consists of tetramers of S4 symmetry, but in trimethylthallium the difference between the intra- and intertetrameric TI ⋯ TI bridge bond-lengths (5·46 ± 0·01 and 5·63 ± 0·01 Å) is much smaller than in trimethylindium (5·235 and 5·665 Å). The co-ordination about the thallium is a distorted trigonal bipyramid with three short equatorial and two long axial bonds.