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Obridge distances are 1.750(7) and 1.743(6) A. The other GeO distances, by comparison, averaged 1.785(7) A. 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) A. 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.