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Ruthenium-Catalyzed Metathesis Reactions of ortho- and meta-Dialkenyl-Carboranes: Efficient Ring-Closing and Acyclic Diene Polymerization Reactions

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journal contribution
posted on 05.07.2010, 00:00 by Marta Guron, Xiaolan Wei, Patrick J. Carroll, Larry G. Sneddon
The ruthenium-catalyzed metathesis reactions of dialkenyl-substituted ortho- and meta-carboranes provide excellent routes to both cyclic-substituted o-carboranes and new types of main-chain m-carborane polymers. The adjacent positions of the two olefins in the 1,2-(alkenyl)2-o-carboranes strongly favor the formation of ring-closed (RCM) products with the reactions of 1,2-(CH2CHCH2)2-1,2-C2B10H10 (1), 1,2-(CH2CH(CH2)3CH2)2-1,2-C2B10H10 (2), 1,2-(CH2CHSiMe2)2-1,2-C2B10H10 (3), 1,2-(CH2CHCH2SiMe2)2-1,2-C2B10H10 (4), and 1,2-[CH2CH(CH2)4SiMe2]2-1,2-C2B10H10 (5) affording 1,2-(−CH2CHCHCH2−)-C2B10H10 (10), 1,2-[−CH2(CH2)3CHCH(CH2)3CH2−]-1,2-C2B10H10 (11), 1,2-[−SiMe2CHCHSiMe2−]-1,2-C2B10H10 (12), 1,2-[−SiMe2CH2CHCHCH2SMe2−]-C2B10H10 (13), and 1,2-[−SiMe2(CH2)4CHCH(CH2)4SiMe2−]-C2B10H10 (14), respectively, in 72−97% yields. On the other hand, the reaction of 1,2-(CH2CHCH2OC(O))2-1,2-C2B10H10 (6) gave cyclo-[1,2-(1′,8′-C(O)OCH2CHCHCH2OC(O))-1,2-C2B10H10]2 (15a) and polymer 15b resulting from intermolecular metathesis reactions. The nonadjacent positions of the alkenyl groups in the 1,7-(alkenyl)2-m-carboranes, 1,7-(CH2CHCH2)2-1,7-C2B10H10 (7), 1,7-(CH2CH(CH2)3CH2)2-1,7-C2B10H10 (8), and 1,7-(CH2CHCH2SiMe2)2-1,7-C2B10H10 (9), disfavor the formation of RCM products, and in these cases, acyclic diene metathesis polymerizations (ADMET) produced new types of main chain m-carborane polymers. The structures of 3, 9, 11, 12, 13, and 15a were crystallographically confirmed.