Additive-Free Thiodelfuorination of Arenes: A series of four-coordinate group 13 difluoride complexes 1-B, 1-Al and 1-Ga supported by a sterically demanding b-diketiminate ligand was prepared. Initial experiments were conducted to screen a series of conditions for the reaction with pentafluoropyridine with group 13 catalysts using silanes as the terminal reductant. 1-B, 1-Al and 1-Ga were found to be active catalysts for the thiodefluorination of electron-deficient arenes with silicon-based reagents at 10-20 mol% loading, between 60 -160 °C, using a,a,a-trifluorotoluene as a solvent (Figure ). Using Me3Si-SPh as a terminal reagent, pentafluoropyridine could be selectively converted into 2a. A control reaction showed a maximum of 10% conversion for this transformation after 24 h at 100 °C, when carried out in the absence of a catalyst. Focusing on thiodefluorination, a scope of electron-deficient fluorinated aromatics was investigated. A series of substituted perfluoroarenes could be selectively converted into the monosubstituted products 2b-2h. Under more forcing conditions higher levels of substitution of pentafluoropyridine and perfluorotoluene could be achieved (see supporting information for details). Hexafluorobenzene reacted selectively giving 2i the product of 1,4-disubstitution. Similarly, P(C6F5)3 underwent a selective tri-substitution under catalytic conditions to yield 2j which could be crystallographically characterized (Figure ). 2j holds promise as a novel ligand for applications in catalysis. 2-(Perfluorophenyl)pyridine underwent non-selective thioylation to form isomers of 2k, primarily at the 2-and 4-position of the perfluorophenyl ring. This finding suggests that the pyridyl directing group has little control on the reaction arguing against coordination of the substrate to the catalyst expected during Lewis acid catalysts. An electron-deficient poly-fluorinated terphenyl underwent non-selective single and double substitution to form 2l and 2l'. Hexafluoropropene is also reactive under the catalytic conditions, providing a mixture of stereoisomers 2m:2m' from thioylation of the terminal sp 2 C-F bonds along with a side-product 2m" derived from protonation, likely from adventitious water.