IR studies of the activation of C=C bond in alkenes by Cu+ ions in zeolites
IR studies of the activation of C=C bond in alkenes by Cu+ ions in zeolites
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DOI：
10.1021/jp0493428
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发表时间：
2004-11-18
影响因子：
3.3
通讯作者：
Kukulska-Zajac, E
中科院分区：
文献类型：
--
作者：
Datka, J;Kukulska-Zajac, E
红外研究表明，CuX、CuY 和 CuZSM-5 沸石中的 Cu+ 离子能够激活烯烃（乙烯、丙烯、1-丁烯和 2-丁烯）中的 C=C 键。 C=C-带的伸缩频率降低了78-115 cm(-1)，表明双键显着减弱。在乙烯中，由于对称性丧失，当与 Cu+ 相互作用时，红外非活性 C=C 拉伸变为红外活性。 C=C 与烯烃相互作用的谱带被分成两个次极大值，表明 Cu+ 离子在不同程度上激活烯烃。对应于双键附近 =CH2 和 =C-H 基团的 C-H 拉伸、变形和弯曲的 IR 谱带也移至较低频率。在高负载量下，一些 Cu+ 离子能够键合两个烯烃分子。烯烃与 Cu+ 的相互作用非常强，以至于烯烃取代了相对稳定的 Cu+CO 和 Cu+(NO)(2) 中的 CO 和 NO。烯烃与 Cu+ 具有非常强的相互作用，这也可以通过氧环的红外带的大幅移动得到证明，该氧环因与 Cu+ 的相互作用而变形，并且当 Cu+ 被烯烃从环中撤出时发生松弛。 Cu+ 活化烯烃的机制很可能与 NO 活化机制类似，即涉及 Cu+ 的 d 电子向烯烃的 pi* 反键轨道的 pi 回馈。
IR studies show that Cu+ ions in zeolites CuX, CuY, and CuZSM-5 are able to activate C=C bond in alknenes (ethene, propene, but-1-ene, and cis-but-2-ene). The stretching frequency of the C=C- band decreased by 78-115 cm(-1), indicating a significant weakening of the double bond. In ethene, the IR inactive C=C stretching became IR active when interacting with Cu+ as the result of the loss of symmetry. The band of C=C interacting with alkenes was split into two submaxima suggesting that Cu+ ions, activate alkenes to a different extent. The IR bands corresponding to C-H stretching, deformation, and bending of the =CH2 and =C-H groups near the double bond also shifted to lower frequencies. At high loadings, some of the Cu+ ions were able to bond two alkene molecules. The interaction of alkenes with Cu+ was so strong that alkenes replaced CO and NO in relatively stable Cu+CO and Cu+(NO)(2). Very strong interaction of alkenes with Cu+ was also evidenced by a large shift of IR band of oxygen ring which was deformed by the interaction with Cu+ and relaxed when Cu+ was withdrawn from the ring by alkene. Most probably the mechanism of the activation of alkenes by Cu+ is similar to the mechanism of activation of NO, that is, involves the pi-back-donation of d electrons of Cu+ to pi* antibonding orbitals of the alkenes.