title: Substituent effects and supramolecular interactions of titanocene(III) chloride: implications for catalysis in single electron steps.
abstract: The electrochemical properties of titanocene(III) complexes and their stability in THF in the presence and absence of chloride additives were studied by cyclic voltammetry (CV) and computational methods. The anodic peak potentials of the titanocenes can be decreased by as much as 0.47 V through the addition of an electron-withdrawing substituent (CO2Me or CN) to the cyclopentadienyl ring when compared with Cp2TiCl. For the first time, it is demonstrated that under the conditions of catalytic applications low-valent titanocenes can decompose by loss of the substituted ligand. The recently discovered effect of stabilizing titanocene(III) catalysts by chloride additives was analyzed by CV, kinetic, and computational studies. An unprecedented supramolecular interaction between [(C5H4R)2TiCl2](-) and hydrochloride cations through reversible hydrogen bonding is proposed as a mechanism for the action of the additives. This study provides the critical information required for the rational design of titanocene-catalyzed reactions in single electron steps.
authors.affiliation: Kekulé-Institut für Organische Chemie und Biochemie, Universität Bonn , Gerhard Domagk Str. 1, 53121 Bonn, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Gansäuer
authors.forename: Christian
authors.initials: C
authors.lastname: Kube
authors.forename: Kim
authors.initials: K
authors.lastname: Daasbjerg
authors.forename: Rebecca
authors.initials: R
authors.lastname: Sure
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.forename: Godfred D
authors.initials: GD
authors.lastname: Fianu
authors.forename: Dhandapani V
authors.initials: DV
authors.lastname: Sadasivam
authors.forename: Robert A
authors.initials: RA
authors.lastname: Flowers