Alternative syntheses of univalent indium salts including a direct route from indium metal

Protonolysis of indium(I) reagents using an [18]crown-6 poly-ether pre-treated with trifluoromethanesulfonic acid (HOTf) provides an efficient route to the known salt [In([18]crown-6)][OTf] in excellent yield. The analogous reaction employing trifluoroacetic acid (HTFA) allows for the isolation of [In([18]crown-6)][TFA], a monovalent indium complex for which the uncrowned salt is not stable at ambient conditions. The direct treatment of indium metal with HOTf, either in the presence or absence of [18]crown-6, provides a high-yield synthetic approach to univalent indium salts that does not require the use of a pre-existing indium(I) reagent.