Nickel fluoro complexes as intermediates in catalytic cross-coupling reactions

The C-F activation of pentafluoropyridine or 2,3,5,6-tetrafluoropyridine at [Ni(COD)(2)] (COD = 1,5-cyclooctadiene) in the presence of (Pr2PCH2CH2OMe)-Pr-i resulted in the formation of the nickel(II) fluoro bisphosphine complexes trans-[Ni(F)(2-C5NF4){kappa(1)-(P)-((Pr2PCH2CH2OMe)-Pr-i)(2)}](1), trans-[Ni(F)(4-C5NF4){kappa(1)-(P)-((Pr2PCH2CH2OMe)-Pr-i)(2)}] (2) and trans-[Ni(F)(2-C5NHF3){kappa(1)-(P)-((Pr2PCH2CH2OMe)-Pr-i)(2)}] (3). The employment of (Pr2PCH2CH2NMe2)-Pr-i gave the nickel(II) fluoro monophosphine complexes [Ni(F)(2-C5NF4){kappa(2)-(P,N)-(Pr2PCH2CH2NMe2)-Pr-i}] (4), [Ni(F)(4-C5NF4){kappa(2)-(P,N)-(Pr2PCH2CH2NMe2)-Pr-i}] (5) and [Ni(F)(2-C5NHF3){kappa(2)-(P,N)-(Pr2PCH2CH2NMe2)-Pr-i}] (6) instead, in which the amino moiety coordinates at the metal center. In catalytic experiments pentafluoropyridine could be converted into 3,5,6-trifluorodiphenyl-Pyridine (7) and 3,5-difluoro-2,4,6-triphenylpyridine (8) in the presence of PhB(OH)(2) and 5 mol% of a mixture of 1 and 2 (ratio 8:1) or 5 and 4 (ratio 2:1) as catalysts. Additionally 2,3,5,6-tetrafluoropyridine could be converted catalytically into 3,5-difluoro-2,6-diarylpyridines (9: aryl = Ph; 10: aryl = Tol; 11: aryl = 4-(F3C)C6H5; 12: aryl = 4-MeOC6H5) in the presence of boronic acids when 5 mol% of 3 was employed as catalyst. (C) 2012 Elsevier B.V. All rights reserved.