C–H and O2 Activation at a Pt(II) Center Enabled by a Novel Sulfonated CNN Pincer Ligand

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• 作者：David Watts ; Daoyong Wang ; Mackenzie Adelberg ; Peter Y. Zavalij ; Andrei N. Vedernikov
• 刊名：Organometallics
• 出版年：2017
• 出版时间：January 9, 2017
• 年：2017
• 卷：36
• 期：1
• 页码：207-219
• 全文大小：679K
• ISSN：1520-6041

文摘

A novel sulfonated CNN pincer ligand has been designed to support CH and O₂ activation at a Pt(II) center. The derived cycloplatinated aqua complex 7 was found to be one of the most active reported homogeneous Pt catalysts for H/D exchange between studied arenes (benzene, benzene-d₆, toluene-d₈, p-xylene, and mesitylene) and 2,2,2-trifluoroethanol (TFE) or 2,2,2-trifluoroethanol-d; the TON for C₆D₆ as a substrate is >250 after 48 h at 80 °C. The reaction is very selective; no benzylic CH bond activation was observed. The per-CH-bond reactivity diminishes in the series benzene (19) > toluene (p-CH:m-CH:o-CH = 1:0.9:0.2) > xylene (2.9) > mesitylene (1.1). The complex 7 reacts slowly in TFE solutions under ambient light but not in the dark with O₂ to selectively produce a Pt(IV) trifluoroethoxo derivative. The H/D exchange reaction kinetics and results of the DFT study suggest that complex 7, and not its TFE derivatives, is the major species responsible for the arene CH bond activation. The reaction deuterium kinetic isotope effect, k_H/k_D = 1.7, the reaction selectivity, and reaction kinetics modeling suggest that the CH bond cleavage step is rate-determining.