Reduction of the tethered carborane 1,2-μ-(CH2SiMe2CH2)-1,2-closo-C2B10H10 followed by metallation with CpCo} or (p-cymene)Ru} fragments affords both C,Câ²-dimethyl 4,1,2-MC2B10 and 4,1,6-MC2B10 species. DFT calculations indicate that the barriers to isomerisation of both 4-Cp-4,1,2-closo-CoC2B10H12 and 4-(η-C6H6)-4,1,2-closo-RuC2B10H12 to their respective 4,1,6-isomers are too high for this to be the origin of the unexpected formation of 4,1,6-MC2B10 products (in marked contrast to the related isomerisation of 1,2-closo-C2B11H13 to 1,6-closo-C2B11H13), and, indeed, the 4,1,2-species are recovered unchanged from refluxing toluene. Equally, the DFT-calculated profile for the isomerisation of [7,8-nido-C2B10H12]2â to [7,9-nido-C2B10H12]2â suggests that the unexpected formation of 4,1,6-metallacarboranes is unlikely to result from isomerisation of a reduced (nido) carborane following desilylation. Instead, the source of the 4,1,6-MC2B10 compounds is traced to desilylation of 1,2-μ-(CH2SiMe2CH2)-1,2-closo-C2B10H10 by Li or Na prior to reduction. The supraicosahedral metallacarboranes 1,8-Me2-4-Cp-4,1,8-closo-CoC2B10H10, 1,12-Me2-4-Cp-4,1,12-closo-CoC2B10H10 and 1,12-Me2-4-(p-cymene)-4,1,12-closo-RuC2B10H10 are also reported with all new species characterised both spectroscopically and crystallographically.
通过对联结的卡巴烯1,2-μ-(CH2SiMe2CH2)-1,2-closo-C2B10H10进行还原,然后用CpCo}或(p-cymene)Ru}片段进行
金属化,可以得到C,C′-二甲基4,1,2-MC2B10和4,1,6-MC2B10物种。DFT计算表明,4-Cp-4,1,2-closo-CoC2B10H12和4-(η-
C6H6)-4,1,2-closo-RuC2B10H12转变为各自的4,1,6-同分异构体的能量障碍过高,因此这并不是4,1,6-MC2B10产品意外生成的原因(与1,2-closo-C2B11H13转变为1,6-closo-C2B11H13 的相关同分异构化形成明显对比),实际上,4,1,2-物种在回流
甲苯中保持不变。同样,DFT计算的[7,8-nido-C2B10H12]2−到[7,9-nido-C2B10H12]2−的同分异构化的能量轮廓也表明,4,1,6-
金属卡巴烯的意外形成不太可能是由于在去
硅化后还原的(nido)卡巴烯所导致的。相反,4,1,6-MC2B10化合物的来源追溯到在还原之前,Li或Na对1,2-μ-(CH2SiMe2CH2)-1,2-closo-C2B10H10进行去
硅化。此外,还报道了超二十面体
金属卡巴烯1,8-Me2-4-Cp-4,1,8-closo-CoC2B10H10、1,12-Me2-4-Cp-4,1,12-closo-CoC2B10H10和1,12-Me2-4-(p-cymene)-4,1,12-closo-RuC2B10H10,所有新物种均通过光谱学和晶体学进行了表征。