Our research comprises the following topics:
Group 13 hydrides
Borane, stabilized by the bicyclic guanidine hppH, undergoes a thermal B-N dehydrocoupling reaction to give the diborane [H2B(hpp)]2. Catalytic B-B dehydrocoupling gives in high yield [HB(hpp)]2 with a direct B-B bond. We tested several catalysts to find the optimal conditions. With the best catalysts, we achieve complete transformation to [HB(hpp)]2 at 110 °C in less than 40 min.
The [HB(hpp)]2 molecule has a rich chemistry, that we are currently developing in three directions: coordination chemistry, oxidative insertion into the B-B bond and hydride substitution, and synthesis of cationic boron hydrides (see Figure 1).
Figure 1 (designed by Arne Wagner)
Sulphur inserts oxidatively into the B-B bond. Since the reaction proceeds slow, one could see several electron transfer intermediates. The reaction mixture darkens with time, and the colors resemble those of a sunrise (see Figure 1, which was made by Nikola Schulenberg for the cover page of Eur. J. Inorg. Chem.). At the end the color fades.