Mechanism of C-H bond activation of alkyl-substituted benzenes by cationic platinum(II) complexes
Mechanism of C-H bond activation of alkyl-substituted benzenes by cationic platinum(II) complexes
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DOI：
10.1021/om050251m
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发表时间：
2005-07-18
期刊：
影响因子：
2.8
通讯作者：
Bercaw, JE
中科院分区：
文献类型：
--
作者：
Driver, TG;Day, MW;Bercaw, JE
虽然所有甲基和乙基取代的苯都与二亚胺Pt（II）甲基阳离子反应生成eta（3）-苄基产物，但它们并不都通过相同的途径到达那里。对于甲苯和对二甲苯，同位素标记显示，初始活化发生在芳基位置，随后分子间转化为苄基产物。对于乙苯和1，4-二乙基苯，初始活化仅发生在芳基C-H键上，并通过分子内异构化转化为η（3）-苄基产物。只有在空间拥挤的最极端的情况下，一个庞大的二亚胺铂甲基阳离子（Ar = Mes）与三乙基苯的反应，不直接激活的乙基成为优选的芳基激活。
While all methyl- and ethyl-substituted benzenes react with diimine Pt(II) methyl cations to give eta(3)-benzyl products, they do not all get there by the same pathway. For toluene and p-xylene, isotopic labeling shows that initial activation occurs at aryl positions with subsequent intermolecular conversion to the benzyl product. For ethylbenzene and 1,4-diethylbenzene, initial activation takes place exclusively at aryl C-H bonds, and conversion to the eta(3)-benzyl product takes place via intramolecular isomerization. Only in the most extreme case of steric crowding-the reaction of a bulky diimine platinum methyl cation (Ar = Mes) with triethylbenzene-does direct activation of the ethyl group become preferred to aryl activation.