Electronic structure and conformational isomerism of the digermene (tBu2MeSi)2Ge=Ge(SiMetBu2)2 as studied by temperature-dependent Raman and UV–vis spectra and quantum-chemistry calculations

Publication date: Available online 22 April 2019Source: Journal of Organometallic ChemistryAuthor(s): Rinat R. Aysin, Sergey S. Bukalov, Larissa A. Leites, Vladimir Ya Lee, Akira SekiguchiAbstractThe structure of the digermene (tBu2MeSi)2Ge = Ge(SiMetBu2)2 (1) was investigated by experimental (Raman and UV–vis) as well as computational (NCA, TD DFT and QTAIM) methods. Temperature-dependent Raman and UV–vis spectra have demonstrated that 1 does not dissociate into the corresponding germylenes on heating either to 120 °C as a solid or to 80 °C in solution, thus preserving the integrity of its double Ge=Ge bond. Raman and NCA results allowed one to estimate the region of the νGe = Ge vibrational frequency in the spectra of digermenes as 270–340 cm−1. When illuminated with a red laser beam of enhanced power (>5 mW), solid 1 undergoes a transformation followed by disappearance of the νGe = Ge Raman band. This process is evidently photodissociation caused by proximity of the red laser wavelength 632.8 nm to the intrinsic absorption of 1 at 616 nm. Temperature dependence of the Raman spectrum has revealed conformational isomerism in solid digermene 1 due to hindered rotation about the Ge–Si bonds, the conformers differing in mutual disposition of Me and bulky tBu groups.Graphical abstractTemperature dependence of the digermene Raman spectrum reveals conformational isomerism due to hindered rotation about the Ge–Si bonds and also demonstrates...

Source: Journal of Organometallic Chemistry - April 23, 2019 Category: Chemistry Source Type: research