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Synthesis of Pentaalkyl-6-bromo-2,3,4,5-tetracarba-nido-hexaboranes(6)

1996; De Gruyter; Volume: 51; Issue: 6 Linguagem: Inglês

10.1515/znb-1996-0616

1865-7117

Bernd Wrackmeyer, Alexandra Glöckle,

Boron and Carbon Nanomaterials Research

Abstract Peralkylated 2,3,4,5-tetracarba-mdo-hexaboranes(6) 1 react with boron tribromide, BBr 3 , via selective exchange of the alkyl substituent in 6-position to give the corresponding new 6- bromo derivatives 2 in quantitative yield. The 6-iodo derivatives 2(1) can be prepared in the same way using BI 3 . Treatment of the carbaboranes 2 with Li Et 3 BH leads to the 1,2,3,4,5- pentaalkyl-2,3,4,5-tetracarba-inido-hexaboranes(6) 3. 1,3,4,6-Tetraethyl-2,3,4,5-tetracarbaw do-hexaborane(6) 4 reacts with BBr 3 via degradation of the carbaborane cage to give EtBBr 2 , and (Z)-1,4-bis [bis(dibromoboryl)]-3-hexene 5. A new bis(diethylboryl)-substituted dialkenyl(bromo)borane 8 was prepared, but attem pts failed to convert it into a 1-bromo- or 6-bromo-mdo-C 4 B 2 -carbaborane. Treatment of 1,1-dialkyl-3-diethylboryl-4-ethylstannoles 9 with a large excess of BBr 3 also affords 5, whereas 6-bromo-l,3,4-triethyl-2,3,4.5-tetracarbamdo- hexaborane(6) 11 was isolated in low yield (<5%) from the reaction between 9 and BBr 3 (slight excess)