Reaction Intermediates Kinetics in Solution Investigated by Electrospray Ionization Mass Spectrometry: Diaurated Complexes

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• 作者：Lucie Ja拧铆kov谩 ; Mariarosa Anania ; Simona Hybelbauerov谩 ; Jana Roithov谩
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：October 28, 2015
• 年：2015
• 卷：137
• 期：42
• 页码：13647-13657
• 全文大小：581K
• ISSN：1520-5126

文摘

A new method to investigate the reaction kinetics of intermediates in solution by electrospray ionization mass spectrometry is presented. The method, referred to as delayed reactant labeling, allows investigation of a reaction mixture containing isotopically labeled and unlabeled reactants with different reaction times. It is shown that we can extract rate constants for the degradation of reaction intermediates and investigate the effects of various reaction conditions on their half-life. This method directly addresses the problem of the relevance of detected gaseous ions toward the investigated reaction solution. It is demonstrated for geminally diaurated intermediates formed in the gold mediated addition of methanol to alkynes. Delayed reactant labeling allows us to directly link the kinetics of the diaurated intermediates with the overall reaction kinetics determined by NMR spectroscopy. It is shown that the kinetics of protodeauration of these intermediates mirrors the kinetics of the addition of methanol demonstrating they are directly involved in the catalytic cycle. Formation as well as decomposition of diaurated intermediates can be drastically slowed down by employing bulky ancillary ligands at the gold catalyst; the catalytic cycle then proceeds via monoaurated intermediates. The reaction is investigated for 1-phenylpropyne (Ph鈥揅C鈥揅H₃) using [AuCl(PPh₃)]/AgSbF₆ and [AuCl(IPr)]/AgSbF₆ as model catalysts. Delayed reactant labeling is achieved by using a combination of CH₃OH and CD₃OH or Ph鈥揅C鈥揅H₃ and Ph鈥揅C鈥揅D₃.