Synthesis and Reactivity of the Fluoro Complex trans-[Pd(F)(4-C5NF4)(iPr2PCH2CH2OCH3)2]: C-F Bond Formation and Catalytic C-F Bond Activation Reactions

The reaction of [Pd(Me)(2)(tmeda)] (tmeda = N,N,N',N'-tetramethylethylendiamine) with the phosphine (Pr2PCH2CH2OCH3)-Pr-i resulted in the formation of the palladium(0) complex [Pd(Pr2PCH2CH2OCH3)(2)] (1). Treatment of 1 with pentafluoropyridine at room temperature yielded the C-F activation product trans-[Pd(F)(4-C5NF4)-((Pr2PCH2CH2OCH3)-Pr-i)(2)] (2). The triflato and bromo complexes trans-[Pd(OTf)(4-C5NF4)((Pr2PCH2CH2OCH3)-Pr-i)(2)] (4) and trans-[Pd(Br)(4-C5NF4)((Pr2PCH2CH2OCH3)-Pr-i)(2)] (5) could be prepared on reaction of complex 2 with EtOTf or 3-bromopropene, respectively. Treatment of 2 with Me3SiCl or HBpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane, pinacolborane) effects the formation of trans-[Pd(Cl)(4-C5NF4)((Pr2PCH2CH2OCH3)-Pr-i)(2)] (6) and trans-[Pd(H)(4-C5NF4)-((Pr2PCH)-Pr-i,CH2OCH3)(2)] (7). In catalytic experiments pentafluoropyridine could be converted into the 4-aryl-tetrafluoropyridines (8, aryl = Ph; 9, aryl = Tol) and into 2,3,5,6-tetrafluoropyridine in the presence of the boronic acids PhB(OH)(2), TolB(OH)(2), or HBpin when 5 mol % of 2 is employed as catalyst.