Carba-closo-dodecaborates with One or Two Alkynyl Substituents Bonded to Boron

Salts of the carba-closo-dodecaborate anion with one or two phenyl- or trimethylsilylalkynyl substituents were synthesized by Pd-catalyzed Kumada-type cross-coupling reactions of the corresponding iodinated clusters with alkynyl Grignard reagents. Selective monofunctionalization in the 7- and 12-position of the {closo-CB11} cluster was achieved, resulting in salts of the anions: [1-R-12-R'C C-closo-CB11H10](-) (R = H, Ph; R' = Ph, Me3Si (1-4)), [12-Hal-7-PhC C-closo-CB11H10]- (Hal = F (5), Cl (6), Br (7)), and [12-F-7-Me3SiC=C-closo-CB11H10](-) (8). Furthermore, the disubstituted derivatives [7,12-(RC C)(2)-Closo-CB11H10](-) (R = Ph (9), Me3Si (10)) are described. All salts were characterized by multi-NMR, IR, and Raman spectroscopy as well as by mass spectrometry (MALDI). The crystal structures of Cs(+)1 and [Et4N](+)6 were determined by single-crystal X-ray diffraction. The spectroscopic and structural properties are compared to values derived from DFT calculations and to data of related boron species with alkynyl groups.