From C-F Activation to Catalytic Regioselective Hydrodefluorination of Pyridines with a Bench-Stable Nickel Complex

The nickel(0) complex [Ni(iPrPN)(COD)] (iPrPN = 2-[(N-diisopropylphosphino)methylamino]pyridine, COD = 1,5-cyclooctadiene) was an efficient precatalyst for the hydrodefluorination of pyridines employing pinacolborane (HBPin). 2-fluoro and 2,6-difluoropyridines were hydrodefluorinated at the 2- and 6-positions under mild condi-tions. Mechanistic experiments allowed to identify COD decoordination followed by C-F activation as the catalyst en-try pathway to the cycle and the [Ni(iPrPN)(COD)] complex as the catalyst resting-state. The Ni(II) fluoride complex, [NiF(iPrPN)(6-Fpy)] (6-Fpy = 6-fluoropyrid-2-yl), was identified as an intermediate in the cycle and a bench-stable precatalyst for the process.