Abstract
Abstract“GaOTf” is a simple, convenient source of low‐valent gallium for synthetic chemistry and catalysis. However, little is currently known about its composition or reactivity. In this work, 71Ga NMR spectroscopy shows the presence of [Ga(arene)n]+ salts on oxidation of Ga metal with AgOTf in arene solvents. However, a more complex picture of speciation is uncovered by X‐ray diffraction studies. In all cases, mixed‐valence compounds containing Ga‐arene and Ga‐OTf coordination motifs, in addition to an unusual “naked” [Ga]+ ion, are found. Addition of 18‐crown‐6 allows for the isolation of a discrete GaI crown complex. Evidence of a potential intermediate in the formation of “GaOTf” has been isolated in the form of the bimetallic silver(I)/gallium(I) cluster anion [Ag4{Ga(OTf)3}4(μ‐Ga)6(OTf)4]2−.
Highlights
Gallium occupies a fascinating position in Group 13
Schneider et al recently reported the preparation of a new low-valent gallium reagent “GaOTf” (OTf = [O3SCF3]À) using a similar route to the preparation of [Ga(arene)n]+[Al(OC(CF3)3)4]À salts,[5a] where gallium metal is oxidized by AgOTf in arene solvents, or dioxane in the presence of 18-crown-6.[8]. “GaOTf” solutions were used as ambiphilic catalysts for CÀC bond forming reactions (Figure 1)
While “GaOTf” solutions are very promising reagents for the emerging field of low-valent Ga catalysis, care is required when considering catalytic mechanisms, as the complex speciation in these systems mean that it may not always be obvious what the catalytically active metal and/or oxidation state will be
Summary
Gallium occupies a fascinating position in Group 13. Much of its chemistry is dominated by the + 3 oxidation state, like the lighter elements, but it displays an extensive range of low oxidation state compounds. Schneider et al recently reported the preparation of a new low-valent gallium reagent “GaOTf” (OTf = [O3SCF3]À) using a similar route to the preparation of [Ga(arene)n]+[Al(OC(CF3)3)4]À salts,[5a] where gallium metal is oxidized by AgOTf in arene solvents, or dioxane in the presence of 18-crown-6.[8] “GaOTf” solutions were used as ambiphilic catalysts for CÀC bond forming reactions (Figure 1).
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