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首页> 外文期刊>Organometallics >Crossover Studies of Methyl Migration from Oxygen to Iron in the Iron-Manganese Methoxycarbyne Complex Cp(CO)Fe(mu-COCH_3)(mu-CO)Mn(CO)MeCp
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Crossover Studies of Methyl Migration from Oxygen to Iron in the Iron-Manganese Methoxycarbyne Complex Cp(CO)Fe(mu-COCH_3)(mu-CO)Mn(CO)MeCp

机译：铁锰甲氧卡宾络合物Cp（CO）Fe（mu-COCH_3）（mu-CO）Mn（CO）MeCp中甲基从氧迁移到铁的交叉研究

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Thermal decomposition of the iron-manganese methoxycarbyne Cp(CO)Fe(mu-CO)(mu-COCH_3)Mn(CO)MeCp(la)occurs to give MeCpMn(CO)_3 and in low yield CpFe(CO)_2CH_3;in the presence of PPh_3,CpFe(CO)(PPh_3)CH_3(2a)forms in high yield.The reaction is first-order in carbyne,but a side reaction that is also first-order in phosphine occurs to give [Cp-(CO)Fe(M-CO)_2Mn(CO)MeCp]~-[CH_3PPh_3]~+(3a)as a byproduct.Crossover experiments between la and its bis-MeCp,CD_3 analogue Ib-d_3 result in scrambling of the methoxycarbyne methyl label between the products 2a and the MeCp analogue 2b.No alkyl exchange is seen in recovered starting materials in the reaction between la and bis-MeCp analogue 3b or(except after prolonged reaction)between the products 2a and 2b-d_3."Control crossover"experiments between la and 2b-d_3 give complete alkyl scrambling.The data prove that alkyl exchange occurs among products after carbyne decomposition and presumably is induced by an intermediate that is formed by carbyne decomposition.Previous results show that the 16-electron intermediate CpFe(CO)CH_3 forms at essentially the same rate from 2a as from la,ruling it out as the exchange intermediate since 2a and 2b-d_3 undergo only very slow exchange.A speculative proposal for the reactive intermediate is that it is the isomeric terminal methoxycarbyne CpFe(ident to)COCH_3,and alkyl migration from oxygen to iron occurs after cluster cleavage.A detailed kinetic scheme for alkyl scrambling is proposed and tested by computer modeling:using an iterative procedure that couples numerical integration of the proposed rate equations with a simplex minimization algorithm designed to find the best rate constants,concentration data from several runs could be quantitatively fit to the proposed mechanism.
机译：铁锰甲氧碳炔Cp（CO）Fe（mu-CO）（mu-COCH_3）Mn（CO）MeCp（1a）的热分解发生，生成MeCpMn（CO）_3且收率低，CpFe（CO）_2CH_3; in PPh_3，CpFe（CO）（PPh_3）CH_3（2a）的形成以高收率形成。该反应在carbyne中是一级反应，但在膦中也发生了一级反应的副反应，生成了[Cp-（CO ）Fe（M-CO）_2Mn（CO）MeCp]〜-[CH_3PPh_3]〜+（3a）.la与bis-MeCp，CD_3类似物Ib-d_3的交叉实验导致甲氧碳炔甲基标记混乱在1a和bis-MeCp类似物3b之间的反应中或在产物2a和2b-d_3之间的反应中（除非经过长时间反应），在回收的起始原料中未观察到烷基交换。 la和2b-d_3之间的实验给出了完整的烷基加扰。数据证明，烷基交换发生在碳炔分解后的产物之间，并且大概是由碳炔形成的中间体诱导的。先前的结果表明16电子中间体CpFe（CO）CH_3从2a形成的速率与从la形成的速率基本相同，并将其作为交换中间体排除在外，因为2a和2b-d_3仅经历非常缓慢的交换。由于中间体是甲氧基碳炔的同分异构体CpFe（与COCH_3相同），因此在发生簇分裂后，烷基会从氧迁移到铁。提出了详细的加扰动力学方案，并通过计算机建模进行了测试：使用迭代程序结合了拟议的速率方程的数值积分和旨在找到最佳速率常数的单纯形最小化算法，可以将来自多次运行的浓度数据定量地拟合至拟议的机制。

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