Germanium Complexes with ONO Tridentate Ligands: O-H Bond Activation Control According to DFT Calculations

Abstract

Polydentate ligands are used for thermodynamic stabilization of tetrylenes—low-valent derivatives of Group 14 elements (E = Si, Ge, Sn, Pb). This work shows by DFT calculations how the structure (the presence or absence of substituents) and type (alcoholic, Alk, or phenolic, Ar) of tridentate ligands 2,6-pyridinobis(1,2-ethanols) [AlkONOR]H2 and 2,6-pyridinobis(1,2-phenols) [ArONOR]H2 (R = H, Me) may affect the reactivity or stabilization of tetrylene, indicating the unprecedented behavior of Main Group elements. This enables the unique control of the type of the occurring reaction. We found that unhindered [ONOH]H2 ligands predominantly led to hypercoordinated bis-liganded {[ONOH]}2Ge complexes, where an E(+2) intermediate was inserted into the ArO-H bond with subsequent H2 evolution. In contrast, substituted [ONOMe]H2 ligands gave [ONOMe]Ge: germylenes, which may be regarded as kinetic stabilized products; their transformation into E(+4) species is also thermodynamically favorable. The latter reaction is more probable for phenolic [ArONO]H2 ligands than for alcoholic [AlkONO]H2. The thermodynamics and possible intermediates of the reactions were also investigated.

Structural Motifs in Aryl Organogermanium Ge-O Derivatives for Material Design

“…At the same time, the effect of organic electron-withdrawing substituents on the Ge atom in related compounds strongly affects the structure of the molecule (causing a change in conformation; as a rule, a decrease in the values of valent bonds and angles; packing in more ordered structures) [25], which makes it important to study the impact of electron-withdrawing substituents on the structure and properties of the Ge-O-Ge molecule. This article is a continuation of our research program [26][27][28] on the effect of substituents on group 14 element derivatives on their structures and properties.…”