Redetermination of tetrakis(trimethylstannyl)germane

Redetermination of the structure of the title compound, [Ge(SnMe3)4] or [GeSn4(CH3)12], previously refined from powder diffraction data only [Dinnebier, Bernatowicz, Helluy, Sebald, Wunschel, Fitch & van Smaalen et al. (2002 ▶). Acta Cryst. B58, 52–61], confirms that four bulky trimethylstannyl ligands surround the central Ge atom (site symmetry 1) in a tetrahedral coordination.

viable low-temperature CVD precursors of Group IV alloys with highly metastable compositions and structures that cannot be obtained by conventional growth routes.
The central Ge atom is tetrahedrally coordinated with four Me 3 Sn ligands. The average Ge-Sn distance of 2.5934 (8) Å agrees well with the predicted value of 2.5680 Å for a Ge(SnH 3 ) 4 analogue (Chizmeshya et al., 2003). In the previous structure determination using powder data, estimated standard deviations for bond lengths and angles are given as 0.04 Å and 0.1°, respectively. In the current determination, an improvement in precision for the structure can be seen in the Ge-Sn core bond lengths, which range from 2.5912 (7) to 2.5953 (8) Å, and bond angles, which range from 107.59 (3) to 111.09 (3) °.

Experimental
After addition of GeH 4 (0.1 g; 1.3 mmol) to Me 3 SnNMe 2 (1.0 g; 5 mmol) at −196 °C, the mixture was warmed to room temperature and stirred for 24 h. The volatiles were identified as HNMe 2 and small amounts of GeH 4 by gas phase IR spectroscopy and were removed at room temperature in vacuo.

GeH 4 + 4 Me 3 SnNMe 2 => Ge[Sn(CH 3 ) 3 ] 4 + 4 HNMe 2
The white solid was recrystallized from a saturated toluene solution at −20 °C and the purity was confirmed by matching the IR spectrum, powder XRD pattern, 1H NMR spectrum, and melting point with the published data (Dinnebier et al., 2002;Wrackmeyer & Bernatowicz, 1999). This represents a simpler alternative than the multistepped reaction, hydrolysis, and separation procedure required with the reaction of Me 3 SnLi and GeCl 4 in tetrahydrofuran. Larger crystals, suitable for single-crystal XRD, were grown by subliming the pure powder in a sealed quartz tube held at 100 °C on one end and room temperature on the other. In contrast, sublimation at 135 °C in vacuo yields only microcrystalline powders.

Refinement
H atoms were positioned geometrically and refined using a riding model, with C-H = 0.96 Å and U iso (H) = 1.5 times U eq (C). as large as those based on F, and R-factors based on ALL data will be even larger.