Electrophilic Methylation of Decaborane(14): Selective Synthesis of Tetramethylated and Heptamethylated Decaboranes and Their Conjugated Bases.

The paper reports specific syntheses of methylated decaborane(14), -BH (), derivatives. The reaction of with an excess of neat MeI and AlCl yields 1,2,3,4-Me--BH () essentially quantitatively when performed at room temperature. Heating the same mixture to 120 °C provides 1-I-2,3,4,5,7,8,10-Me--BH (). The formation of analogous 1-CFSOO-2,3,4,5,7,8,10-Me--BH () is achieved by heating or with an excess of MeSOCF in the presence of a catalytic amount of HOSOCF to 120 °C. Compounds and can be deprotonated to yield the corresponding anions [1,2,3,4-Me--BH] (), [1-I-2,3,4,5,7,8,10-Me--BH] (), and [1-CFSOO-2,3,4,5,7,8,10-Me--BH] (). The structure of all the compounds isolated has been unambiguously confirmed by multinuclear (B and H) NMR measurements, and the structures of , , , and have been established by X-ray diffraction analyses. The very high volatility of has made it impossible to apply X-ray diffraction in this case; therefore, its structure has been derived computationally using the ab initio/GIAO/NMR tool. DFT-based computational protocols have also outlined the reason why it is impossible to obtain an octamethyl derivative of experimentally.