title: Dibenzosilanorbornadienyl cations and their fragmentation into silyliumylidenes.
abstract: The terphenyl-substituted dibenzosilanorbornadienyl cation 11 was synthesized and isolated in the form of its [B(C6F5)4](-) salt. The salt was characterized by NMR spectroscopy supported by quantum mechanical computations and by an XRD analysis of a corresponding acetonitrilium salt. The thermal fragmentation of 11[B(C6F5)4] in benzene results in the high-yield formation of diphenylterphenylsilylium borate 17[B(C6F5)4]. High-lying intermediates in this process are solvent-complexed terphenylsilyliumylidene 8 and the hydrogen- and phenyl-substituted silylium ion 20. The formation of silylium ion 20 by reaction of silyliumylidene 8 with the solvent benzene demonstrates the high potential of this four valence electron species in C-H bond activation reactions. In addition, the instability of the hydrogen-substituted silylium ion 20 in benzene opens new mechanistic perspectives particular for dihydrogen activation by silyl cationic frustrated Lewis pairs and in general for the dihydrogen activation by strong Lewis acids.
authors.affiliation: Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Strasse 9-11, D-26129 Oldenburg, Federal Republic of Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Gerdes
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Saak
authors.forename: Detlev
authors.initials: D
authors.lastname: Haase
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
mesh_terms: D001881:Borates / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D001881:Borates; D017646:Organosilicon Compounds