Synthesis of a Bench-Stable Manganese(III) Chloride Compound: Coordination Chemistry and Alkene Dichlorination

The complex [MnCl₃(OPPh₃)₂] (1) is a bench-stable and easily prepared source of MnCl₃. It is prepared by treating acetonitrile solvated MnCl₃ (2) with Ph₃PO and collecting the resulting blue precipitate. 1 is useful in coordination reactions by virtue of the labile Ph₃PO ligands, and this is demonstrated through the synthesis of {Tpm*}MnCl₃ (3). In addition, methodologies in synthesis that rely on difficult or cumbersome to prepare solutions of reactive MnCl₃ can be accomplished using 1 instead. This is demonstrated through alkene dichlorinations in a wide range of solvents, open to air, and with good substrate scope. Light-accelerated halogenation and radical sensitive experiments support a radical mechanism involving stepwise Cl-atom transfer(s) from 1.