title: Buttressing effects on haloarene deprotonation: a merely kinetic or also thermodynamic phenomenon?
abstract: (2,6-Dichlorophenyl)- and (2,6-dibromophenyl)trialkylsilanes undergo hydrogen/metal interconversion preferentially at the 4- rather than 3-position. However, the organometallic species generated by such a "meta metalation" are thermodynamically less stable (i.e., more basic) than those that would result from an ordinary "ortho metalation". This was demonstrated by equilibration experiments based on permutational halogen/metal interconversion. A new buttressing effect can explain the unprecedented regioselectivity. It is supported by X-ray structures that reveal marked deformations of the benzene ring in halophenylsilanes. [structure: see text]
authors.affiliation: Institute of Chemical Sciences and Engineering (ISIC), Ecole Polytechnique Fédérale, (BCh), CH-1015 Lausanne, Switzerland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Gorecka
authors.forename: Christophe
authors.initials: C
authors.lastname: Heiss
authors.forename: Rosario
authors.initials: R
authors.lastname: Scopelliti
authors.forename: Manfred
authors.initials: M
authors.lastname: Schlosser