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[3.3.3.01,5]undecane (1), 1-isopropoxy-3,3,7,7-tetramethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.01,5]undecane (2), and 1-isopropoxy-3,3-dimethyl-2,8,9-trioxa-5-aza-1-germatricyclo[3.3.3.01,5]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.

Graphical abstractNovel germatrane complexes with methyl substituents in the atrane cage were prepared. X-ray analysis revealed that the coordination around Ge was a slightly distorted trigonal bipyramidal geometry and three five-membered rings adopted an envelope conformation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Trialkanolamine ligands (HOCH2CH2)nN(CH2CMe2OH)3−n (n = 0–2) were used as a ligand. ► Ge(O-i-Pr)4 was used as a metal precursor. ► Monomeric germatrane complexes were prepared. ► X-ray analysis revealed that three five-membered rings adopt an envelope conformation.