Kinetic studies indicate that trans-[FeH(H2)(dppe)2]+ reacts with an excess of NEt3 to form cis-[FeH2(dppe)2] in a single kinetic step. The second-order rate constant is strongly affected by the presence of added salts, an acceleration being observed with BF4- and PF6- salts and a deceleration with BPh4-. Theoretical calculations indicate that the role of the accelerating anions consists of the formation of ion pairs that provide a more effective reaction pathway for deprotonation. However, for the ionpair with the bulky BPh4- anion, steric crowding in the proximities of the dihydrogen ligand hinders the approach of the base, and the reaction is decelerated. Copyright © 2004 American Chemical Society.
Basallote, M. G., Besora, M., Durán, J., Fernández-Trujillo, M. J., Lledós, A., Angeles Máñez, M., & Maseras, F. (2004). The Effect of the "Inert" Counteranions in the Deprotonation of the Dihydrogen Complex trans-[FeH(η<sup>2</sup>-H<inf>2</inf>)(dppe) <inf>2</inf>]<sup>+</sup>: Kinetic and Theoretical Studies. Journal of the American Chemical Society, 126(8), 2320-2321. https://doi.org/10.1021/ja039844j