Reaction of the [arachno-4-NB8H12]− anion 2 with [RhCl2(η5-C5Me5)]2 in CH2Cl2 at room temperature affords a mixture of red ‘6,9’ isomer [9-(η5-C5Me5)-nido-6,9-NRhB8H11] (3) and its yellow ‘6,8’ isomer, [8-(η5-C5Me5)-nido-6,8-NRhB8H11] (4). Under the same conditions, reactions of 2 with [IrCl2(η5-C5Me5)]2 and [RuCl2(η6-MeC6H4-4-isoPr)]2 give the ‘6,8’ isomers, yellow [8-(η5-C5Me5)-nido-6,8-NIrB8H11] (5) and red [8-(η6-MeC6H4-4-isoPr)-nido-6,8-NRuB8H11] (6), respectively. In contrast, [IrCl(PPh3)3] yields orange [9,9-(PPh3)2-9-H-nido-6,9-NIrB8H11] (7), which exhibits the ‘6,9’ configuration. Compound 3 isomerizes quantitatively in solution to give 4. At high temperatures, compound 7 gives the yellow ‘6,8’ species, [8,8-(PPh3)2-8-H-nido-6,8-NIrB8H11] (8), in low yields. Possible mechanisms for the unprecedented 6,9 → 6,8 isomerization are discussed.
[arachno-4-NB8H12]− 阴离子 2 与 [RhCl2(η5-C5Me5)]2 在
CH2Cl2 中于室温下反应,得到红色“6,9”异构体 [9-(η5-C5Me5)-nido- 的混合物6,9-NRhB8H11] (3) 及其黄色“6,8”异构体,[8-(η5-C5Me5)-nido-6,8-NRhB8H11] (4)。在相同条件下,2与[IrCl2(η5-C5Me5)]2和[RuCl2(η6-MeC6H4-4-isoPr)]2反应得到'6,8'异构体,黄色[8-(η5-C5Me5)分别为-nido-6,8-NIrB8H11] (5) 和红色[8-(η6-MeC6H4-4-isoPr)-nido-6,8-NRuB8H11] (6)。相比之下,[IrCl(PPh3)3] 产生橙色 [9,9-(PPh3)2-9-H-nido-6,9-NIrB8H11] (7),呈现“6,9”构型。化合物 3 在溶液中定量异构化,得到 4。在高温下,化合物 7 得到黄色“6,8”物质,[8,8-(PPh3)2-8-H-nido-6,8-NIrB8H11] (8 ),产量低。讨论了前所未有的 6,9 → 6,8 异构化的可能机制。