Mechanism of Hydrogenolysis of an Iridium鈥揗ethyl Bond: Evidence for a Methane Complex Intermediate

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• 作者：Jes煤s Campos ; Sabuj Kundu ; Dale R. Pahls ; Maurice Brookhart ; Ernesto Carmona ; Thomas R. Cundari
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：January 30, 2013
• 年：2013
• 卷：135
• 期：4
• 页码：1217-1220
• 全文大小：290K
• 年卷期：v.135,no.4(January 30, 2013)
• ISSN：1520-5126

文摘

Evidence for key 蟽-complex intermediates in the hydrogenolysis of the iridium鈥搈ethyl bond of (PONOP)Ir(H)(Me)⁺ (1) [PONOP = 2,6-bis(di-tert-butylphosphinito)pyridine] has been obtained. The initially formed 畏²-H₂ complex, 2, was directly observed upon treatment of 1 with H₂, and evidence for reversible formation of a 蟽-methane complex, 5, was obtained through deuterium scrambling from 畏²-D₂ in 2-d₂ into the methyl group of 2 prior to methane loss. This sequence of reactions was modeled by density functional theory calculations. The transition state for formation of 5 from 2 showed significant shortening of the Ir鈥揌 bond for the hydrogen being transferred; no true Ir(V) trihydride intermediate could be located. Barriers to methane loss from 2 were compared to those of 1 and the six-coordinate species (PONOP)Ir(H)(Me)(CO)⁺ and (PONOP)Ir(H)(Me)(Cl).