Hypervalent benzophenones

Publication date: Available online 31 January 2018 Source:Journal of Organometallic Chemistry Author(s): Evgeniya P. Doronina, Valery F. Sidorkin, Elena F. Belogolova, Viatcheslav Jouikov Benzophenones (BPs) of the type 2-R-BP and 2,2′-R-BP, carrying silicon- or germanium-containing substituents R (R = EY2X; E = Si, Ge; Y = H, Me, F, Cl; X = H, F, Cl, OTf) at one or at two ortho-positions of the arene rings, were theoretically designed. Among 26 compounds considered, only 10 mono-substituted 2-R-BP and 5 bis-substituted 2,2′-R-BP (in hexane and DMSO solutions) belong to the first examples of hypervalent benzophenones. In these “true” chelates, the length of the O→E dative contact (which has a covalent component, according to the AIM analysis) is in the range of 2.0–2.4 Å, and the degree of pentacoordination of E is higher than 40%. In these compounds, a significant planarization of the benzophenone part occurs, compared to the initial BP. The TD-DFT calculations suggest the UV spectral properties of the hypervalent BPs to differ fundamentally from those of BP. For the “true” chelates 2-R-BP and 2,2′-R-BP, there is a well pronounced trend of a change of the coordination O→E contact strength along with the difference between the wavelengths of their first high-intensity band and the ππ* band of the unsubstituted BP.

Source: Journal of Organometallic Chemistry - January 31, 2018 Category: Chemistry Source Type: research