Copyright © 2014 John Wiley & Sons, Ltd. The structure and dynamics of five-coordinate iridacyclopentadiene-chlorido and -hydrido complexes of the form [(PH 3 ) 2 Ir(CY = CYCY′ = CY′)X] (X = Cl or H and Y = F and/or H) are investigated by M06-2X/Def2-TZVPP density functional theory computation. For the symmetrically substituted ring systems (Y = Y′ = H and Y = Y′ = F) the minimum energy chlorido structures are Y-shaped trigonal bipyramids; whereas the hydrido complexes favor a T-structure. Both the symmetrically and unsymmetrically (Y = H, Y′ = F) substituted hydrido complexes exhibit double well potentials for the hydrido ligand wag motion within the metallacycle ring plane, the depths of the well depending on the degree of steric, and electronic interactions within the particular constitutional isomer.

Sly silyl caught in the act: Protonation of a mesitylene ring by the strongly acidic arenium carborane [CH(3)C(6)H(6)]- [CHB(11)Me(5)Br(6)] initiates a cascade reaction that results in a stable beta-silyl allyl cation (see picture, H yellow, C blue, silyl allyl group red). Remarkably, the driving force in the reaction suffices to disrupt a stable aromatic ring in favor of a cationic reactive intermediate.

Si(mply) rips it apart: C-F activation of fluorobenzene has been achieved using the extremely strong silyl Lewis acids [Et3Si(X)]+ (X=PhF or Et3SiH) and [(2,6-dixylyl-C6H 3)SiMe2] + paired with the anion CHB 11Cl11-. They abstract fluoride from unactivated fluorobenzene to give arylated products, consistent with phenyl-cation-like reactivity (see scheme). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.