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Selectivity in Adduct Formation of a Bidentate Boron Lewis Acid
J Louis Beckmann1, Beate Neumann1, Hans-Georg Stammler1
1Chair of Inorganic and Structural Chemistry, Center for Molecular Materials CM2 Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany.
Abstract:
A bidentate boron Lewis acid based on 1,8-diethynylanthracene has been studied in detail with respect to its adduct formation with diamines and diphosphanes of different linker lengths between the donor functions. A clear correlation between the linker length of the bifunctional base and the formation of 1 : 1 adducts, 1 : 2 adducts or oligomers was found. The adducts were characterized in solution by NMR titration experiments and structurally by X-ray diffraction. In addition, adduct formation and competition experiments of the host system with ZR3 (Z=N, P; R=H, Me) demonstrated the generally higher stability of alkylphosphane adducts compared to alkylamine adducts with boron functions. The results provide a general insight into the adduct formation of bidentate Lewis acids with guests of different sizes as well as the differences in stability between borane-amine and borane-phosphane adducts.
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