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The reaction of [Pd(Me) 2 (tmeda)] (tmeda = N,N,N′,N′-tetramethylethylendiamine) with the phosphine i Pr 2 PCH 2 CH 2 OCH 3 resulted in the formation of the palladium(0) complex [Pd( i Pr 2 PCH 2 CH 2 OCH 3 ) 2 ] (1). Treatment of 1 with pentafluoropyridine at room temperature yielded the C−F activation product trans-[Pd(F)(4-C 5 NF 4 )-( i Pr 2 PCH 2 CH 2 OCH 3 ) 2 ] (2). The triflato and bromo complexes trans-[Pd(OTf)(4-C 5 NF 4 )( i Pr 2 PCH 2 CH 2 OCH 3 ) 2 ] (4) and trans-[Pd(Br)(4-C 5 NF 4 )( i Pr 2 PCH 2 CH 2 OCH 3 ) 2 ] (5) could be prepared on reaction of complex 2 with EtOTf or 3-bromopropene, respectively. Treatment of 2 with Me 3 SiCl or HBpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane, pinacolborane) effects the formation of trans-[Pd(Cl)(4-C 5 NF 4 )( i Pr 2 PCH 2 CH 2 OCH 3 ) 2 ] (6) and trans-[Pd(H)(4-C 5 NF 4 )-( i Pr 2 PCH 2 CH 2 OCH 3 ) 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.

The hydrido complexes trans-[Pd(H)(4-C(5)NF(4))(PiPr(3))(2)] (3) and trans-[Pd(H)(4-C(5)NF(4))(PCy(3))(2)] (5) can be prepared by reaction of trans-[Pd(F)(4-C(5)NF(4))(PiPr(3))(2)] (2) or trans-[Pd(F)(4-C(5)NF(4))(PCy(3))(2)] (4) with HBpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane, pinacolborane). The iodo and triflato complexes trans-[Pd(I)(4-C(5)NF(4))(PiPr(3))(2)] (7) and trans-[Pd(OTf)(4-C(5)NF(4))(PiPr(3))(2)] (9) are generated on treatment of complex 3 with MeI or ethyltrifluoromethanesulfonate (EtOTf), respectively. Treatment of 3 with Ph(3)CPF(6) in MeCN results in the formation of trans-[Pd(4-C(5)NF(4))(NCMe)(PiPr(3))(2)]PF(6) (6a). Heating 3 to 60 degrees C gives the products of reductive elimination 2,3,5,6-tetrafluoropyridine as well as [Pd(PiPr(3))(2)] (1). In the presence of pentafluoropyridine [Pd(PiPr(3))(2)] (1) affords the oxidative addition product 2. In a catalytic experiment, pentafluoropyridine can be converted into 2,3,5,6-tetrafluoropyridine in the presence of HBpin with 44% yield when 10% of 3 is employed as catalyst.

The use of carboxylates in the carbodiimide-mediated coupling to amines was investigated. The addition of pyridinium ptoluenesulfonate (PPTS) and a tertiary amine was found to significantly improve acylation yields by up to 70%.

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