DIRECTIVE EFFECTS IN BRIDGE CLEAVAGE REACTIONS OF METHYL-SUBSTITUTED BORON HYDRIDES .1. PREPARATION AND NUCLEAR MAGNETIC-RESONANCE SPECTRA OF 3-CH3B6H11, 3-CH3B6H10, AND 1-CH3B4H9

Procedures have been developed for preparing certain specifically methyl-substituted boron hydrides: 3-CH3B6H11, 3-CH3B5H10, and 1-CH3B4H9. The methyl-substituted derivative of B6H12, 3-CH3B6H11, is prepared by adding BH3 to 1-CH3B5H7-followed by protonation with HC1. Starting with 3-CH3B6H11, the lower hydrides are prepared through the following sequence of steps: (1) cleavage of the bridge system with ammonia yielding [BH2(NH3)2+][3-CH3B5H9-]; (2) protonation of the anion with liquid HCl yielding 3-CH3B5H10. The same sequence applied to 3-CH3B5H10 yields 1-CH3B4H9. A directive effect appears to be operative in the cleavage reactions. In each case, boron atoms farthest from the methyl group are split off from the framework. The methyl-substituted boron hydrides 3-CH3B6Hu, 3-CH3B5H10, and 1-CH3B4H9 appear to be more stable than the parent hydrides B6H12, B5HU, and B4H10. © 1979, American Chemical Society. All rights reserved.