ИСТИНА

The structure and chemical behavior of metallatranes, N(CH2CH2O)3M-X (A) – cyclic derivatives of trialkanolamines – have been extensively studied, and compounds of elements have been reported all over the periodic table. These derivatives usually contain a transannular interaction between metal atom and the bridgehead nitrogen atom. Most of the previous extensive work on metallatranes has been focused on the synthesis, physico-chemical properties and X-ray studies of these compounds in order to confirm the supposed intramolecular N→M coordination. Here we present the synthesis, crystal structure, and electronic properties of the first germanium compound, N(CH2CH2O)3Ge–Ge(SiMe3)3 (I), with non-constrained hypercoordination of germanium atom bounded to another germanium atom which is unusual in terms of a chemical species prepared to date. The germatrane I was found to be stable even under gas phase (mass-spectrometry study). The structure of I was confirmed by NMR spectroscopy and X-ray crystallographic analysis. Its electronic structure was characterized by ultraviolet–visible spectroscopy and density functional theory (DFT) calculations to reveal their unique electronic properties. The calculations were performed with full geometry optimization and used the GAUSSIAN’03 program package. Additional single-point calculations have been carried out for Ge dimers using the binding energy partition scheme implemented in the ADF program. The calculated at B3LYP/DGDZVP level of the theory germanium-nitrogen (2.570 Å), germanium-oxygen (1.850 Å), germanium-silicon (2.424 Å) and germanium-germanium (2.458 Å) distances and valence Ge-Ge-N) angle (176.5) for atrane close to experimental values. It is well known that the DFT approach tends to underestimate the strength of atom-atom interaction in such kind of system. However, in this case a good agreement between theory (B3LYP/DGDZVP) and experiment (accurate solid phase structural data for atrane) was found. The calculated at the BP86/TZ2P+ level in gas phase UV-spectra give the bands close to 234 and 225 nm that indicates to the σ→σ* transitions. We can see from Fig. 1 that these transitions are from HOMO (electron density is mainly the [Si(Me3)]3 groups with small contribution on the Ge- Ge bond) to LUMO+1 and LUMO+2 (anti-bonding Ge-Ge bond). The calculated at B3LYP/6- 311+G(2d,p) level of the theory 1H, 13C and 29Si chemical shits are close to experimental ones.