Exceedingly facile Ph−X activation (X=Cl, Br, I) with ruthenium(II) : Arresting kinetics, autocatalysis, and mechanisms
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[(Ph3P)3Ru(L)(H)2] (where L=H2 (1) in the presence of styrene, Ph3P (3), and N2 (4)) cleave the Ph[BOND]X bond (X=Cl, Br, I) at RT to give [(Ph3P)3RuH(X)] (2) and PhH. A combined experimental and DFT study points to [(Ph3P)3Ru(H)2] as the reactive species generated upon spontaneous loss of L from 3 and 4. The reaction of 3 with excess PhI displays striking kinetics which initially appears zeroth order in Ru. However mechanistic studies reveal that this is due to autocatalysis comprising two factors: 1) complex 2, originating from the initial PhI activation with 3, is roughly as reactive toward PhI as 3 itself; and 2) the Ph[BOND]I bond cleavage with the just-produced 2 gives rise to [(Ph3P)2RuI2], which quickly comproportionates with the still-present 3 to recover 2. Both the initial and onward activation reactions involve PPh3 dissociation, PhI coordination to Ru through I, rearrangement to a η2-PhI intermediate, and Ph[BOND]I oxidative addition.
Miloserdov , F M , McKay , D , Muñoz , B K , Samouei , H , Macgregor , S A & Grushin , V V 2015 , ' Exceedingly facile Ph−X activation (X=Cl, Br, I) with ruthenium(II) : Arresting kinetics, autocatalysis, and mechanisms ' , Angewandte Chemie International Edition , vol. 54 , no. 29 , pp. 8466–8470 . https://doi.org/10.1002/anie.201501996
Angewandte Chemie International Edition
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DescriptionThe ICIQ Foundation and The Spanish Government (Grant CTQ2011-25418 and the Severo Ochoa Excellence Accreditation 2014-2018 SEV-2013-0319) are thankfully acknowledged for support of this work. F.M.M. is grateful to the Government of Spain (MICINN) for the FPI Ph.D. Scholarship (BES-2012-054922). S.A.M. and D.M. thank the EPSRC for support through award EP/J010677/1.
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