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首页> 外文期刊>Chemistry: A European journal >The importance of a single methyl group in determining the reaction chemistry of pentamethylcyclopentadienyl cyclooctatetraenyl uranium metallocenes
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The importance of a single methyl group in determining the reaction chemistry of pentamethylcyclopentadienyl cyclooctatetraenyl uranium metallocenes

机译：单个甲基在确定五甲基环戊二烯基环辛酸酯四烯基铀金属茂的反应化学中的重要性

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The steric factors that allow trivalent [(C_5Me_5) _3U] (1) to function as a three-electron reductant with C _8H_8 to form tetravalent [{(C_5Me _5)(C_8H_8)U}_2(μ-C_8H _8)] (2) have been explored by examining the synthesis and reactivity of the intermediate, "[(C_5Me_5)_2(C _8H_8)U]" (3), and the slightly less crowded analogues, [(C_5Me_5)(C_5Me_4H)(C _8H_8)U] and [(C_5Me_4H) _2(C_8H_8)U], that have, successively one less methyl group. The reaction of [{(C_5Me_5)(C _8H_8)U(μ-OTf)}_2] (4; OTf=OSO _2CF_3) with two equivalents of KC_5Me_5 in THF gave ring-opening to "[(C_5Me_5)(C _8H_8)U{O(CH_2)_4(C_5Me _5)}]" consistent with in situ formation of 3. Reaction of 4 with two and four equivalents of KC_5Me_4H generates two equivalents of [(C_5Me_5)(C_5Me _4H)(C_8H_8)U] (5) and [(C_5Me _4H)_2(C_8H_8)U] (6), respectively, which in contrast to 3 were isolable. Tetravalent 5 reduces phenazine and PhEEPh (E=S, Se, and Te) to form the tetravalent uranium reduction products, [{(C _5Me_5)(C_8H_8)U}_2(μ- C_(12)H_8N_2)] (7), [{(C_5Me _5)(C_8H_8)U}_2(μ-SPh)_2] (8), [{(C_5Me_5)(C_8H_8)U} _2(μ-SePh)_2] (9), and [{(C_5Me _5)(C_8H_8)U}_2(μ-TePh)_2] (10), consistent with sterically induced reduction. In contrast, the less sterically crowded 6 does not react with these substrates. What a difference a methyl makes! Attempts to synthesize [(C_5Me_5) _2(C_8H_8)U], [(C_5Me _5)(C_5Me_4H)(C_8H_8)U], and [(C_5Me_4H)_2(C_8H_8)U] from [{(C_5Me_5)(C_8H_8)U(OSO _2CF_3)}_2] with KC_5Me_5 and KC_5Me_4H allowed isolation only of the last two complexes, which differ in reactivity as shown in the scheme.
机译：允许三价[[C_5Me_5）_3U]（1）与C _8H_8形成三价电子还原剂以形成四价[[（（C_5Me _5）（C_8H_8）U} _2（μ-C_8H_8）]的位阻因子（2 ）已通过检查中间体“ [[C_5Me_5）_2（C _8H_8）U]”（3）和稍稍拥挤的类似物[[C_5Me_5）（C_5Me_4H）（C _8H_8）U的合成和反应性进行了探索]和[（C_5Me_4H）_2（C_8H_8）U]依次少一个甲基。 [{（C_5Me_5）（C _8H_8）U（μ-OTf）} _ 2]（4; OTf = OSO _2CF_3）与两当量的KC_5Me_5在THF中的反应使环开环为“ [[C_5Me_5）（C _8H_8） U {O（CH_2）_4（C_5Me _5）}]“与3的原位形成一致。4与2和4个当量的KC_5Me_4H反应生成2个[[C_5Me_5）（C_5Me _4H）（C_8H_8）U]的当量。 5）和[（C_5Me _4H）_2（C_8H_8）U]（6），与3相反。四价5还原吩嗪和PhEEPh（E = S，Se和Te）形成四价铀还原产物[[（（C _5Me_5）（C_8H_8）U} _2（μ-C_（12）H_8N_2）]（7）， [{（C_5Me _5）（C_8H_8）U} _2（μ-SPh）_2]（8），[{（C_5Me_5）（C_8H_8）U} _2（μ-SePh）_2]（9）和[{（C_5Me _5）（C_8H_8）U} _2（μ-TePh）_2]（10），与空间诱导还原反应一致。相反，空间较少拥挤的6不与这些基板反应。甲基有什么不同！尝试从[{（C_5Me_5）（C_8H）[带有KC_5Me_5和KC_5Me_4H的OSO _2CF_3）} _ 2]允许仅隔离最后两种复合物，它们的反应性不同，如方案所示。

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