Reactions of the nido-carborane salts (Bu4N)(nido-7,9-R,Râ²-7,9-C2B9H10) (R,Râ²
= H; R,Râ²
= Me; R,Râ²
= Ph; R = Ph, Râ²
= Me) with H2SO4 at ambient temperature give the 11-vertex closo-carboranes 2,3-R,Râ²-2,3-C2B9H9 in high yields (R,Râ²
= H; R,Râ²
= Me; R,Râ²
= Ph; R = Ph, Râ²
= Me). Halogenated derivatives of closo-carboranes, 10-X-2,3-C2B9H10 (X = Cl, I), are formed from reactions of salts containing 1(6)-X-7,9-C2B9H11â anions with H2SO4, and 4-F-2,3-(p-FC6H4)2-2,3-C2B9H8 is formed from (Bu4N)(3-F-7,9-(p-FC6H4)2-7,9-C2B9H9) and F3CSO3H. Elimination of the ethoxide and fluoride substituents from the cage occurs during acidification of salts containing 10-OEt-7,9-C2B9H11â and 10-F-7,9-(p-FC6H4)2-7,9-C2B9H9â by F3CSO3H, resulting in the closo-carboranes 2,3-C2B9H11 and 2,3-(p-FC6H4)2-2,3-C2B9H9 as major products respectively. A mixture of B-Me-2,3-C2B9H10 isomers is obtained from salts containing the 8-Me-7,9-C2B9H11â and 10-Me-7,9-C2B9H11â anions with H2SO4. B-Me-2,3-C2B9H10 is suggested to be fluxional in solution with 4-Me-2,3-C2B9H10 as the major component. Protonation of the fluxional anion 10(11)-endo-Me-7,9-C2B9H11â with acetic acid gives a neutral nido-carborane 11-Me-2,8-C2B9H12 rather than closo-B-Me-2,3-C2B9H10. Molecular geometries of 11-vertex closo-carboranes and B-methyl-nido-carboranes are determined by the combined ab initio/GIAO/NMR method at the GIAO-B3LYP/6-311G*//MP2/6-31G* level of theory.
尼多
硼烷盐 (Bu4N)(尼多-7,9-R,Râ²-7,9-C2
B9H10)(R,Râ² = H; R,Râ² = Me; R,Râ² = Ph;R,Râ²=H;R,Râ²=Me;R,Râ²=Ph;R=Ph,Râ²=Me)与 H2SO4 在常温下反应,得到 11-蝶形的闭合
硼烷 2,3-R,Râ²-2,3-C2
B9H9,产量很高(R,Râ²=H;R,Râ²=Me;R,Râ²=Ph;R=Ph,Râ²=Me)。含有 1(6)-X-7,9-C2
B9H11â 阴离子的盐与 H2SO4 反应生成 10-X-2,3-C2
B9H10(X = Cl,I)的闭
硼烷卤代衍
生物,而 4-F-2,3-(p-FC6H4)2-2,3-C2
B9H8 则由 (Bu4N)(3-F-7,9-(p-FC6H4)2-7,9-C2
B9H9) 和 F3CSO3H 生成。在用 F3CSO3H 酸化含有 10-OEt-7,9-C2
B9H11â 和 10-F-7,9-(p-FC6H4)2-7,9-C2
B9H9â 的盐的过程中,笼中的乙
氧基和
氟化取代基会被消除,主要产物分别为 2,3-C2
B9H11 和 2,3-(p-FC6H4)2-2,3-C2
B9H9。用 H2SO4 与含有 8-Me-7,9-C2
B9H11â 和 10-Me-7,9-C2
B9H11â 阴离子的盐反应,可以得到 B-Me-2,3-C2
B9H10 异构体的混合物。据认为,B-Me-2,3-C2
B9H10 在溶液中具有通性,其主要成分是 4-Me-2,3-C2
B9H10。通性阴离子 10(11)-endo-Me-7,9-C2
B9H11â 与
乙酸发生质子化反应后,得到的是中性的 nido-
硼烷 11-Me-2,8-C2
B9H12,而不是封闭的 B-Me-2,3-C2
B9H10。在 GIAO-B3LYP/6-311G*//MP2/6-31G* 理论
水平上,通过 ab initio/GIAO/NMR 组合方法确定了 11-vertex闭合
硼烷和 B-
甲基-nido-
硼烷的分子几何结构。