A mechanistic investigation of carbon-hydrogen bond stannylation: synthesis and characterization of nickel catalysts

作者：Johnson Samuel A^*; Doster Meghan E; Matthews Jacob; Shoshani Manar; Thibodeau Michelle; Labadie Amanda; Hatnean Jillian A

来源：Dalton Transactions, 2012, 41(26): 8135-8143.

DOI：10.1039/c2dt30310h

The complex ((Pr3P)-Pr-i)Ni(eta(2)-Bu3SnCH=CH2)(2) (1a) was characterized by NMR spectroscopy and was identified as the active species for catalytic C-H bond stannylation of partially fluorinated aromatics, for example in the reaction between pentafluorobenzene and Bu3SnCH=CH2, which generates C6F5SnBu3 and ethylene. The crystalline complex ((Pr3P)-Pr-i)Ni(eta(2)-Ph3SnCH=CH2)(2) (1b) provides a more easily handled analogue, and is also capable of catalytic stannylation with added Ph3SnCH=CH2 and C6F5H. Mechanistic studies on 1b show that the catalytically active species remains mononuclear. The rate of catalytic stannylation is proportional to [C6F5H] and inversely proportional to [Ph3SnCH=CH2]. This is consistent with a mechanism where reversible Ph3SnCH=CH2 dissociation provides ((Pr3P)-Pr-i)Ni(eta(2)-Ph3SnCH=CH2), followed by a rate-determining reaction with C6F5H to generate the stannylation products. Kinetic competition reactions between the fluorinated aromatics pentafluorobenzene, 1,2,4,5-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene and 1,3-difluorobenzene all suggest significant Ni-aryl bond formation in the rate-determining step under catalytic conditions. Labelling studies are consistent with an insertion of the hydrogen of the arene into the vinyl group, followed by beta-elimination or beta-abstraction of the SnPh3 moiety.

• 出版日期2012