The Structure of Bis(catecholato)silanes: Phase Adaptation by Dynamic Covalent Chemistry of the Si–O Bond

• Published in: Journal of the American Chemical Society 2021-11, Vol.143 (44), p.18784-18793
• Main Authors: Hartmann, Deborah, Thorwart, Thaddäus, Müller, Rosa, Thusek, Jean, Schwabedissen, Jan, Mix, Andreas, Lamm, Jan-Hendrik, Neumann, Beate, Mitzel, Norbert W, Greb, Lutz
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.1c09746

Catechols occupy a unique role in the structural, bio-, and geochemistry of silicon. Although a wealth of knowledge exists on their hypercoordinate complexes, the structure of tetracoordinate bis­(catecholato)­silane, Si­(catH)2 1, has been enigmatic since its first report in 1951. Indeed, the claim of a planar-tetracoordinated silicon in 1 triggered a prominent debate, which is unsettled to this day. Herewith, we present a comprehensive structural study on 1 and derivatives in the gas phase by electron diffraction, in a neon matrix by IR spectroscopy, in solution by diffusion NMR spectroscopy, and in the solid-state by X-ray diffraction and MAS NMR spectroscopy, complemented by high-level quantum-chemical computations. The compound exhibits unprecedented phase adaptation. In the gas phase, the monomeric bis­(catecholato)­silane is tetrahedral, but in the condensed phase, it is metastable toward oligomerization up to a degree controllable by the type of catechol, temperature, and concentration. For the first time, spectroscopic evidence is obtained for a rapid Si–O σ-bond metathesis reaction. Hence, this study sorts out a long-lasting debate and confirms dynamic covalent features for our Earth’s crust’s most abundant chemical bond.