Affiliations: Laboratoire de Chimie et Biochimie des Complexes Moléculaires, UMR CNRS 7576, Ecole Nationale Supérieure de Chimie de Paris, 11 rue Pierre et Marie Curie, 75005 Paris, France | Institut de Chimie UMR CNRS 7177, Institut Le Bel, Université Louis Pasteur, 4 rue Blaise Pascal, 67000 Strasbourg, France
Abstract: The Ga dimethyl complexes {6-(CH2NMe2)-2-R-C6H3O}GaMe2 (2a, R = Me; 2b, R = Ph; 2c, R = tBu) are readily accessible via a classical alkane elimination reaction between the corresponding aminophenol ligand and GaMe3. In the case of 2a, X-ray crystallographic studies clearly establish this species as monomeric and with the Ga center being η2-chelated by one aminophenolate moiety. The ionization reaction of complexes 2a – c with B(C6F5)3 affords the corresponding dinuclear Ga cationic adducts {6-(CH2NMe2)-2-R-C6H3O} GaMe·{6-(CH2NMe2)-2-R-C6H3O}GaMe2 + (3a+, R = Me; 3b+, R = Ph; 3c+, R = tBu) as fully dissociated MeB(C6F5)3 salts. On the basis of thorough 1D and 2D NMR studies, the Ga cations 3a – c+ appear to be structurally similar to their Al analogs, which were previously X-ray characterized. The ionization reaction of 2c by B(C6F5)3 (room temperature, CH2Cl2) yields a thermodynamic equilibrium (with the Ga cation 3c+ as the major product under the studied conditions) as deduced from low temperature NMR experiments, which shows that the Me– abstraction reaction performed by B(C6F5)3 at a Ga center may occur in a reversible way. The reaction of compounds 2a – c with 1 equiv. of PhOH provides access to the corresponding mono-methyl Ga complexes {6-(CH2NMe2)-2-R-C6H3O}Ga(Me)(OPh) (4a, R = Me; 4b, R = Ph ; 4c, R = tBu), which, unlike 2a – c, do not undergo any ionization reaction when reacted with [Ph3C][B(C6F5)4] or B(C6F5)3.
Keywords: Gallium complexes, Cations, Aminophenolate, Lewis acids
