Mechanism of the Dehydrogenative Silylation of Alcohols Catalyzed by Cationic Gold Complexes: An Experimental and Theoretical Study

Abstract

The catalytic activity both of cationic [(XDPP)Au][X] (XDPP = bis-2,5-diphenylphosphole xantphos X = BF(4)) and of the isolated gold hydride complex [(XDPP)(2)Au(2)H][OTf] in the dehydrogenative silylation process is presented. A parallel theoretical study using density functional theory revealed a mechanism involving the counter anion as a co-catalyst, which was experimentally confirmed by testing various counterions (X = OTf, NTf(2), PF(6)). Finally, a "Au(2)H(+)" species was determined as the intermediate during the catalytic cycle, which correlates well with the experimental findings on the first example of catalytic activity of an isolated "Au-H" complex.

Fundamental Elementary Steps in Gold Chemistry

“…However, this is not the only modus operandi; a notable exception is the gold-catalyzed dehydrogenative silylation of alcohols, involving gold-hydride species [157][158][159][160].…”

Cooperative Catalysis: Electron‐Rich FeH Complexes and DMAP, a Successful “Joint Venture” for Ultrafast Hydrogen Production

“…[2] The latter aspect is of particular interest for applications in which varying amounts of energy are required at defined timely events (e.g., in the automotive industry [3] ). Various catalytic systems are known to catalyze this reaction, [7] but not all of them do meet the requirement for the HOD technology, that is, the tunable generation of a defined amount of H 2 gas within seconds from a storage medium that possesses a high hydrogen content while employing abundant and affordable catalysts. Fast dehydrogenative silylation using readily available alcohols appears to be one of the most promising chemical approaches to solve this problem.…”

“…Fast dehydrogenative silylation using readily available alcohols appears to be one of the most promising chemical approaches to solve this problem. Various catalytic systems are known to catalyze this reaction, [7] but not all of them do meet the requirement for the HOD technology, that is, the tunable generation of a defined amount of H 2 gas within seconds from a storage medium that possesses a high hydrogen content while employing abundant and affordable catalysts. Furthermore, the silylether can be recycled by a simple hydride reduction.…”

Ein thermisch stabiles Gold(III)‐Hydrid: Synthese, Reaktivität und reduktive Kondensation als Weg zu Gold(II)‐Komplexen

“…B. heterogene Goldkatalysatoren für selektive Hydrierungen eingesetzt, [5] und für Gold-Hydrierungskatalysatoren auf Zirconiumoxidträgern wurden Au 3+ -Ionen als aktive Zentren vorgeschlagen. [6] Gold(I)-und Gold(III)-Hydride wurden als Zwischenstufen zahlreicher homogenkatalysierter Prozesse postuliert, wie Hydrierungen, [7,8] Hydrosilylierungen, [9] dehydrierende Alkohol-Silylierungen, [10] Hydroborierungen [11] und andere organische Reaktionen. [12] Corma und Mitarbeiter verwendeten immobilisierte Gold-(III)-Chelatkomplexe als Hydrierungskatalysatoren und untersuchten die Rolle von Gold(III)-Hydriden detailliert mit kinetischen Methoden und Modellrechnungen.…”