A Brønsted Acidic Gallium Hydride: Facile Interconversion of NNNN‐Macrocycle Supported [GaI]+ and [GaIIIH]2+

Angewandte Chemie International Edition, vol. 61, pp. e202114629

Abstract

Abstract Protonolysis of [Cp*M] (M=Ga, In, Tl) with [(Me4TACD)H][BAr4Me] (Me4TACD=N,N′,N′′,N′′′‐tetramethyl‐1,4,7,10‐tetraazacyclododecane; [BAr4Me]−=[B{C6H3‐3,5‐(CH3)2}4]−) provided monovalent salts [(Me4TACD)M][BAr4Me], whereas [Cp*Al]4 yielded trivalent [(Me4TACD)AlH][BAr4Me]2. Protonation of [(Me4TACD)Ga][BAr4Me] with [Et3NH][BAr4Me] gave an unusually acidic (pKa(CH3CN)=24.5) gallium(III) hydride dication [(Me4TACD)GaH][BAr4Me]2. Deprotonation with IMe4 (1,3,4,5‐tetramethyl‐imidazol‐ylidene) returned [(Me4TACD)Ga][BAr4Me]. These reversible processes occur with formal two‐electron oxidation and reduction of gallium. DFT calculations suggest that gallium(I) protonation is facilitated by strong coordination of the tetradentate ligand, which raises the HOMO energy. High nuclear charge of [(Me4TACD)GaH]2+ facilitates hydride‐to‐metal charge transfer during deprotonation. Attempts to prepare a gallium(III) dihydride cation resulted in spontaneous dehydrogenation to [(Me4TACD)Ga]+.

Authors 6

1. Louis J. Morris Aachen Institute for Inorganic Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute for Inorganic Chemistry RWTH Aachen University 52062 Aachen Germany

2. Priyabrata Ghana Aachen Institute for Inorganic Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute for Inorganic Chemistry RWTH Aachen University 52062 Aachen Germany

3. Thayalan Rajeshkumar

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Université de Toulouse · Institut National des Sciences Appliquées de Toulouse · Laboratoire de Physique et Chimie des Nano-Objets

   Affiliation as printed

   CNRS INSA UPS UMR 5215 LPCNO Université de Toulouse 135 Avenue de Rangueil 31077 Toulouse France

4. Ambre Carpentier

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Université de Toulouse · Institut National des Sciences Appliquées de Toulouse · Laboratoire de Physique et Chimie des Nano-Objets

   Affiliation as printed

   CNRS INSA UPS UMR 5215 LPCNO Université de Toulouse 135 Avenue de Rangueil 31077 Toulouse France

5. Laurent Maron corresponding

   Centre National de la Recherche Scientifique · Université Toulouse III - Paul Sabatier · Université de Toulouse · Institut National des Sciences Appliquées de Toulouse · Laboratoire de Physique et Chimie des Nano-Objets

   Affiliation as printed

   CNRS INSA UPS UMR 5215 LPCNO Université de Toulouse 135 Avenue de Rangueil 31077 Toulouse France

6. Jun Okuda corresponding Aachen Institute for Inorganic Chemistry

   RWTH Aachen University

   Affiliation as printed

   Institute for Inorganic Chemistry RWTH Aachen University 52062 Aachen Germany