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Reactions of the Ni(0) Compound Ni(PPh3)4with Unactivated Alkyl Halides: Oxidative Addition Reactions Involving Radical Processes and Nickel(I) Intermediates by Ryley Kehoe; Markshun Mahadevan; Adeela Manzoor; Gillian McMurray; Patrick Wienefeld; Michael C. Baird; Peter H. M. Budzelaar is a Chemistry article available to read on EtoBox.

What is Reactions of the Ni(0) Compound Ni(PPh3)4with Unactivated Alkyl Halides: Oxidative Addition Reactions Involving Radical Processes and Nickel(I) Intermediates about?

Reactions of the nickel(0) compound NiL 4 (L = PPh 3 ) with alkyl halides RX involve initial inner-sphere halogen atom abstraction from the alkyl halides to form alkyl radicals R• and halonickel(I) metalloradical species NiX(PPh 3 ) 2,3 . The radical pairs then undergo combination within the solvent cage to give the square planar nickel(II) compounds NiRX(PPh 3 ) 2 . Radical intermediacy is demonstrated persuasively by observations that the relative rates vary in the orders tert-butyl > sec-butyl > n-butyl and RI > RBr > RCl, while density functional theory calculations indicate that the radical mechanism provides a lower energy pathway than do alternative, more conventional pathways. The product of the reaction of Ni(PPh 3 ) 4 with methyl iodide, NiMeI(PPh 3 ) 2 , decomposes in solution to ethane and NiI(PPh 3 ) 2,3 , but when RX = EtI, n-BuI, sec-BuI, tert-BuI, the alkyl-nickel products undergo rapid β-hydrogen elimination to give the hydride NiHI(PPh 3 ) 2 plus the corresponding alkene(s). Reactions also occur in which a portion of the alkyl radicals diffuses from the solvent cage and abstracts hydrogen from NiHI(PPh 3 ) 2 to form alkanes RH and Ni(I) species NiI(PPh 3 ) 2 . As

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Author

Ryley Kehoe; Markshun Mahadevan; Adeela Manzoor; Gillian McMurray; Patrick Wienefeld; Michael C. Baird; Peter H. M. Budzelaar

Published

2018

Language

EN

Field

Chemistry (Physical Sciences)