Date: December 24, 2012
Creator: Mei, Jiajun; Carsch, Kurtis M.; Freitag, Cody R.; Gunnoe, T. Brent & Cundari, Thomas R., 1964-
Description: This article discusses variable pathways for oxygen atom insertion into metal-carbon bonds. Abstract: Cp*W(O)₂(CH₂SiMe₃) (1) (Cp* = η⁵-pentamethylcyclopentadienyl) reacts with oxygen atom donors (e.g., H₂O₂, PhIO, IO₄⁻) in THF/water to produce TMSCH₂OH (TMS = trimethylsilyl). For the reaction of 1 with IO₄⁻, the proposed pathway for alcohol formation involves coordination of IO₄⁻ to 1 followed by concerted migration of the -CH₂TMS ligand to the coordinated oxygen of IO₄⁻ with concomitant dissociation of IO₃⁻ to produce Cp*W(O)₂(OCH₂SiMe₃) (3), which undergoes protonolysis to yield free alcohol. In contrast to the reaction with IO₄⁻, the reaction of 1 with H₂O₂ results in the formation of the η²-peroxo complex Cp*W(O)(η²-O₂)(CH₂SiMe₃) (2). In the presence of acid (HCl) or base (NaOH), complex 2 produces TMSCH₂OH. The conversion of 2 to TMSCH₂OH catalyzed by Brønsted acid is proposed to occur through protonation of the η²-peroxo ligand, which facilitates the transfer of the -CH₂TMS ligand to a coordinated oxygen of the η²-hydroperoxo ligand. In contrast, the hydroxide promoted conversion of 2 to TMSCH₂OH is proposed to involve hydroxide coordination, followed by proton transfer fro the hydroxide ligand to the peroxide ligand to yield a κ¹-hydroperoxide intermediate. The migration of the -CH₂TMS ligand to the coordinated oxygen of ...
Contributing Partner: UNT College of Arts and Sciences