Synthesis and X-ray diffraction analysis/crystal structure of new germatranes containing methyl substituents in three five-membered chelating rings

Three monomeric germatranes, 1-isopropoxy-3,3,7,7,10,10-hexamethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (1), 1-isopropoxy-3,3,7,7-tetramethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (2), and 1-isopropoxy-3,3-dimethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.0^1,5]undecane (3) have been synthesized by the reaction of Ge(O-i-Pr)₄ in refluxing toluene with corresponding triethanolamines, (HOCH₂CH₂)_nN(CH₂CMe₂OH)_3−n (n = 0, L1H₃; n = 1, L2H₃; n = 2, L3H₃), where the number of CMe₂ groups adjacent to a OH functionality varied from 3 (L1H₃) to 2 (L2H₃), and to 1 (L3H₃). These germatranes 1-3 have been characterized by solution ¹H and ¹³C{¹H} NMR and the solid state structure of 2 has been determined by single crystal X-ray diffraction.     

New synthetic routes to allylic germatranes

Allylic germatranes derived from triethanolamine can be prepared with moderate control of regioselectivity by two complementary routes. The first of these is through the preparation of the precursor allylic germanium trichlorides by a transmetallation reaction between germanium(IV) chloride and the corresponding allylic tributylstannanes followed by alcoholysis and reaction with triethanolamine. The second route is via the palladium-catalyzed hydrogermylation of conjugated dienes by germatrane, N(CH₂CH₂O)₃GeH. The former route gives mixtures of E and Z stereoisomers, whereas the second route gives exclusively Z products.     

Structure of an oxo-bridged germatrane dimer

The reaction of tris(2-hydroxyphenyl)amine with Ge(OEt)₄ produced 1,1′-oxybis(1-germa-5-aza-2,8,9-trioxatribenzobicyclo[3.3.3]undeca-3,6,10-triene) (11). This reaction proceeded via 1-ethoxy-1-germa-5-aza-2,8,9-trioxatribenzobicyclo[3.3.3]undeca-3,6,10-triene (10a). In oxo-bridged germatrane dimer 11, the Ge---O---Ge moiety is bent at an angle of 131.2(4)°, and Ge---O^bridge distances are 1.750(7) and 1.743(6) Å. The other Ge---O distances, by comparison, averaged 1.785(7) Å. The germanium centers in 11 are nearly trigonal bipyramidal by virtue of significant interaction with transannular nitrogen: the Ge---N distances are 2.235(8) and 2.247(7) Å. Ab initio calculations on 11 and H₃Ge---O---GeH₃ predict a linear Ge---O---Ge geometry when d-orbitals are omitted from the basis set, but correctly predict a bent geometry when d-orbitals are used.     

Synthesis and Characterisation of 1‐[9‐(H,Me3Si,Me3Ge,Me3Sn)9‐Fluorenyl]‐3,7,10‐trimethylgermatranes. The Crystal Structure Analysis of 1‐(9‐Fluorenyl)‐3,7,10‐trimethylgermatrane

The title compounds, viz. C₁₃H₈(R)Ge · (OCHMeCH₂)₃N ( 1 : R = H, 2 : R = Me₃Si; 3 : R = Me₃Ge) were prepared as mixtures of diastereomers by the reaction of N(CH₂CHMeOSnAlk₃)₃ ( 7 : Alk = Et; 8 : Alk = Bu) with C₁₃H₈(R)GeBr₃ ( 4 : R = H, 5 : R = Me₃Si; 6 : R = Me₃Ge), respectively. The synthesis of C₁₃H₈(Me₃Sn)Ge · (OCHMeCH₂)₃N ( 13 ) by the reaction of germatrane ( 1 ) with Me₃SnNMe₂ is reported. Identity and structures were established by elemental analyses, ¹H and ¹³C NMR spectroscopy and mass spectrometry. The crystal structure of 1 was determined by X‐ray diffraction methods.     

The crystal and molecular structures of three germatrane derivatives

The molecular and crystal structure of three germatrane compounds: 1-(1-bromobicyclo[4.1.0]hept-7-yl)germatrane, l-(1-trimethylsilanyl-cyclopropyl)-germatrane and 1-(1-Methyl-1,2-dicarba-closo-dodecaboranyl)germatrane has been determined by X-ray diffraction method in order to investigate main geometrical regularities of the germatrane molecules. There were established all values of the main structural parameters above-mentioned molecules.     

Synthesis,characterization, and structures of 1-(9-Fluorenyl)-germatrane and 1-(Phenylacetylenyl)germatrane

Syntheses of the title compounds, viz. N(CH₂CH₂O)₃GeY ( 2 Y?Fluorenyl; 4 Y?PhC?C) by the reaction of X₃GeY ( 1 Y?Fluorenyl, X?Br; 5 Y?PhC?C, X?Cl) with N(CH₂CH₂OSnR₃)₃ ( 3 R?Et; 6 R?Bu) are reported including the preparation of the new compound 1 . Identity and structures were established by elemental analyses, ¹H and ¹³C NMR spectroscopy. 2 and 4 were characterized by mass spectrometry. Single crystal structures of 1 , 2 and 4 were determined by X-ray diffraction methods.     

Bonding in germatranyl cation and germatranes

Equilibrium structures of silatranyl and germatranyl cations as well as corresponding fluoroatranes are obtained at the B3LYP/cc-pVDZ level of theory. Changes in the bonding on going from germatranyl cation to a neutral molecule are analyzed by using the NBO method. In contrast to three-coordinate planar germylium cations, germatranyl cation does not possess a vacant orbital which is involved in the formation of the transannular bond. However, in germatrane upon formation of an “external” bond with a fluorine anion the inversion of this orbital occurs to accept halogen electron pairs. The presence of the GeF bond drastically changes the scheme of bonding in the GeO₃N moiety compared to that of cation through the formation of interactions of a fluorine atom with equatorial oxygens.