Inorganic Chemistry, Vol.49, No.13, 6139-6147, 2010
Ruthenium-Catalyzed Metathesis Reactions of ortho- and meta-Dialkenyl-Carboranes: Efficient Ring-Closing and Acyclic Diene Polymerization Reactions
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)(3)CH2)(2)-1,2-C2B10R10 (2), 1,2-(CH2=CHSiMe2)(2)-1,2-C2B10H10 (3), 1,2-(CH2=CHCH2SiMe2)(2)-1,2-C2B4H10 (4), and 1,2-[CH2=CH(CH2)(4)SiMe2](2)-1,2-C2B10H10 (5) affording 1,2-(-CH2-CH=CHCH2-)-C2B10H10 (10), 1,2-[-CH2(CH2)(3)CH=CH(CH2)(3)CH2-]-1,2-C2B10H10 (11), 1,2-[-SiMe2CH=CHSi-Me-2-]-1,2-C2B10H10 (12), 1,2-[-SiMe2CH2CH=CHCH2SMe2-]-C2B10H10 (13), and 1,2-[-SiMe2(CH2)(4)CH=CH(CH2)(4)SiMe2H-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)(3)CH2)(2)-1,7-C2B10H10 (8), and 1,7-(CH2=CH-CH2SiMe2)(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.