Synthesis, X-ray Diffraction Studies, and DFT Calculations on Hexacoordinated Germanium Derivatives:  The Case of Germaspirobis(ocanes)

Synthesis of the title compounds, viz. [RN(CH₂CHR‘O)₂]₂Ge (1, R = Me, R‘ = H; 2, R = Me, R‘ = Ph; 3, R = Ph, R‘ = H), by the reaction of 2 equiv of corresponding dialkanolamines RN(CH₂CHR‘OH)₂ (4, R = Me, R‘ = H; 5, R = Me, R‘ = Ph; 6, R = Ph, R‘ = H) with (AlkO)₄Ge is reported. Composition and structures of all novel compounds were established by ¹H and ¹³C NMR spectroscopy and mass spectrometry as well as elemental analysis data. The single-crystal X-ray diffraction of 2 has clearly indicated the presence of two transannular interactions Ge←N in the compound. N atoms are cis-orientated. The compound 3 possesses long Ge···N distances. The structural data obtained from geometry optimizations by DFT calculations on 1−3 reproduces experimental results. Both cis- and trans-isomers were studied, and cis-configuration was found to be more thermodynamically stable for all three compounds. The transition states for possible cis ↔ trans rearrangement processes in 1−3 were calculated. The properties of the Ge−O and Ge←N bonds in 1−3 were analyzed by the AIM approach. The interactions between the Ge atom and N atoms as well as O atoms possess predominantly ionic character.