Pentaalkyl-6-Triorganostannyl-2,3,4,5-Tetracarba-Nido-Hexaboranes(6)

Abstract

Pentaalkyl-6-bromo-2,3,4,5-tetracarba-n/cfo-hexaboranes(6) (carb-Br 2) react with trimethylstannyl-and triphenylstannyl-lithium to give the 6-stannyl subtituted carbaboranes carb-SnMe 3 3a and carb-SnPh 3 3b. The reactivity of 3b towards various electrophiles was studied. It reacts with tin tetrachloride and tin tetrabromide preferably by cleavage of the Sn-C bond, leading finally to novel inorganic tin(IV) halides carb-SnCI 3 6(CI) or carb-SnBr 3 6(Br). This is also true for the reaction with boron tribromide. In this case, carb-SnBr 3 6(Br) proved to be stable even in the presence of an excess of BBr 3 ; heating of this mixture at 60°C leads back to 2 and to SnBr 2 . In the reaction with bromine, it appears that both Sn-C and Sn-B bonds are attacked since the formation of carb-SnPh 2 Br 4(Br), carb-SnPhBr 2 5(Br) and 2 can be detected by 119 Sn and 11 B NMR. No reaction of 3b with zirconium tetrachloride was observed, whereas titanium tetrachloride reacts very slowly, aaain by cleavage of one of the Sn-C bonds. All products were characterized by 1 H, 11 B, 13 C and 1 Sn NMR spectroscopy.

One‐Pot Synthesis of 1,6‐Diiodo‐2,3,4,5‐tetracarba‐nido‐hexaboranes(6) and Mechanistic Studies on the Reaction System Alkynes/BI3/NaK2.8

“…They also studied the reactions between the peralkylated 2,3,4,5‐tetracarba‐ nido ‐hexaboranes(6) and an excess of BBr 3 (and BI 3 ), whereby the corresponding B6‐halo substituted carboranes were formed 5b. Nucleophilic substitution reactions of such B‐halo carboranes were found to replace the basal B6‐halogen atom to give the corresponding carboranes with organyl,5c stannyl5d and diphenylphosphanyl5e groups as well as, in the 1,6‐dibromo case, an N ‐bonded [Fe 2 (CO) 6 (μ‐SN)] substituent in the 6‐position 5f. Currently there is no easy pathway to such B‐functionalized C 4 B 2 ‐ nido ‐carboranes.…”