CHEMISTRY OF C-TRIMETHYLSILYL-SUBSTITUTED HETEROCARBORANES .18. SYNTHETIC, SPECTROSCOPIC, REACTIVITY, AND BONDING STUDIES ON THE GROUP 13 ELEMENT METALLACARBORANES - CRYSTAL-STRUCTURES OF -1-(ME(2)CH)-1-IN-2,4-(SIME(3))(2)-2,4-C(2)B(4)H4, AND CH)-1-IN(2,2'-C10H8N2)-2,4-(SIME(3))(2)-2,4-C2B4H4

The reactions of the THF-solvated ''carbons apart'' dilithiacarboranes , Li(THF)](mu-THF)-1-Li-2-(SiMe(3))-4-(R)-2,4,C2B4H4 [R = SiMe(3) (I), Me (II)], with freshly prepared [t-BuGaCl(2)](2) or i-PrInI2 in THF s olution in molar ratios of 1:1 at 0 degrees C produced the correspondi ng closo-gallacarboranes, 1-(CMe(3))-1-Ga-2-(SiMe(3))-4-(R)-2,4-C2B4H4 [R = SiMe(3) (III), Me (IV)], and closo-indacarboranes, 1-[(Me)(2)CH] -1-In-2-(SiMe(3))-4-(R)-2,4-C2B4H4 [R = SiMe(3) (X), Me (XI)], as colo rless liquids or crystalline solids in 53, 59, 35, and 43% yields, res pectively. These closo-metallacarboranes react with 2,2'-bipyridine, 2 ,2'-bipyrimidine, and 2,2':6',2''-terpyridine in benzene solution at r oom temperature to form the corresponding donor-acceptor complexes, (C Me(3))-1-Ga(2,2'-C10H8N2)-2-(SiMe(3))-4-(R)-2,4- C2B4H4 [R = SiMe(3) ( VI), Me (VII)], (3))-1-Ga(2,2'-C8H6N4)-2,4-(SiMe(3))(2)-2,4-C2B4H4 (VI II), CMe(3))-1-Ga(C15H11N3)-2,4-(SiMe(3))(2)-2,4-C2B4H4 (IX), CH]-1-In (2,2'-C10H8N2)-2,4-(SiMe(3))(2)-2,4-C2B4H4 (XII), and )CH]-1-In(2,2'-C 8H6N4)-2,4-(SiMe(3))(2)-2,4,C2B4H4 (XIII), in 40-90% yields. The compo unds II-XIII were all characterized on the basis of H-1, B-11, and C-1 3 NMR spectra, IR spectra, and mass spectra, The compounds VI, VIII, X , and XII were also characterized by single-crystal X-ray analyses. Fo r a comparative study, the 2,2'-bipyridine adduct of the ''carbons adj acent'' gallacarborane, 3))-1-Ga(2,2'-C10H8N2)-2,3-(SiMe(3))(2)-2,3-C2 B4H4 (V), was synthesized and spectroscopically characterized, and its crystal structure was also determined. The crystal structures of V, V I, VIII, and XII show that each complex has a distorted pentagonal bip yramidal geometry, with the group 13 atom occupying the apical positio n and coordinating to the nitrogen atoms of the Lewis bases, whereas t he crystal structure of the indacarborane (X) shows a dimer of two dis torted closo-metallacarborane cages, similar to that found for the car bons adjacent isomer. The compounds V, VI, VIII, X, and XII crystalliz ed in monoclinic or triclinic space groups P2(1)/n, P2(1)/c, P (1) ove r bar, C2/c, and P (1) over bar, respectively, with a = 9.778(2), 12.5 50(4), 9.611(4), 23.288(7), and 9.079(5) Angstrom, b = 25.031(5), 15.8 85(5), 15.813(7), 9.169(7), and 16.127(6) Angstrom, c = 11.376(2), 19. 965(7), 19.808(7), 19.130(5), and 19.83(9) Angstrom, alpha = 90.00, 90 .00, 69.40(3), 90.00, and 88.20(3)degrees, beta = 96.47(2), 103.42(2), 93.81(3), 98.02(2), and 81.75(3)degrees, gamma = 90.00, 90.00, 82.39( 3), 90.00, and 79.21(3)degrees, V = 2766.6(9), 3871(2), 2784(2), 4045( 2), and 2823(3) Angstrom(3) and Z = 4, 4, 4, 4, and 4, respectively. T he final refinements of V, VI, VIII, X, and XII converged at R = 0.041 2, 0.0411, 0.056, 0.029, and 0.0495 and R(w) = 0.0488, 0.0517, 0.057, 0.039, and 0.0698, respectively.