The first example of a catalytically active system for Suzuki-type cross-coupling reactions of perfluorinated arenes such as octafluorotoluene and decafluorobiphenyl is presented.

The reaction of [Ni(COD)2] with stable N-heterocyclic carbenes R2Im (R2Im = 1,3-di(R)imidazole-2-ylidene; R2 = Me2, n Pr2, Me i Pr, i Pr2) affords homoleptic [Ni(Me2Im)3] (1) or dinuclear, COD-bridged complexes of the type [Ni2(R2Im)4(COD)] (R2 = n Pr2, 2; Me i Pr, 3; i Pr2, 4). Compounds 1−4 are suitable precursors for the synthesis of [Ni(R2Im)2]-containing complexes in solution, exemplified by the reaction with CO under atmospheric pressure, with equimolar amounts of diphenyl acetylene or with biphenylene to give carbonyl complexes [Ni(R2Im)2(CO)2] (R2 = Me2, 5; n Pr2, 6; Me i Pr, 7; i Pr2, 8), diphenyl acetylene complexes [Ni(R2Im)2(η2-C2Ph2)] (R2 = Me2, 9; n Pr2, 10; Me i Pr, 11; i Pr2, 12), and biphenylene complexes [Ni(R2Im)2(2,2‘-biphenyl)] (R2 = Me2, 13; n Pr2, 14; Me i Pr, 15; i Pr2, 16). Furthermore, the reaction of 4 with 3-hexyne or 2-butyne afforded [Ni( i Pr2Im)2(η2-C2R2)] (R = Me, 18; Et, 19) in good yields. The compounds 1, 11, 13, 17, and 18 have been structurally characterized. Complexes 13−16 are the products of a stoichiometric carbon−carbon activation of biphenylene, and compounds 1−4 (as well as 9−12) are efficient catalysts for the insertion of diphenyl acetylene into the C−C bond of biphenylene, a process in which the C−C activation of biphenylene is incorporated into a catalytic cycle. The reaction rate of the formation of 9,10-di(phenyl)phenanthrene depends on the nature of the carbene ligand of the catalyst; the highest was observed for [Ni2( i Pr2Im)4(COD)] (4).

The first examples of transition metal mediated C-S cleavage of sulfoxides containing sp2- and sp3-hybridized carbon bonds attached to the sulfur atom and the first example of a structurally characterized complex featuring an oxygen-bound sulfinyl ligand are presented.

[Ni2(iPr2Im)4(COD)] 1 (iPr2Im = 1,3-di(isopropyl)-imidazol-2-ylidene) reacts at room temperature with the thioethers methyl para-tolyl sulfide, ethyl phenyl sulfide, benzothiophene and dibenzothiophene to afford the C-S bond cleavage products [Ni(iPr2Im)2(4-CH3-C6H4)(SMe)] 2, [Ni(iPr2Im)2(C6H5)(SEt)] 3, [Ni(iPr2Im)2(1,8-benzothiophenylato)] 4 and [Ni(iPr2Im)2(C,S-dibenzothiophenylato)] 5. In contrast to the reaction of thioethers or sulfoxides (reported earlier), no C-S bond cleavage was observed for the reaction of 1 with the sulfones bezothiophene-1,1-dioxide and methyl phenyl sulfone. In those cases the stable compounds [Ni(iPr2Im)2(eta2-2,3-benzothiophene-1,1-dioxide)] 6 and [Ni(iPr2Im)2(eta2-MeSO2C6H5)] 7 with a eta2-coordinated sulfone ligand have been isolated. Compound 6 has been structurally characterized. S-H bond cleavage was observed using 2-methyl-2-propanthiol to afford [Ni(iPr2Im)2(H)(StBu)] 8. The reaction of 1 with disulfides led to the dithiolato complexes [Ni(iPr2Im)2(SR)2] (R = tBu 9, Me 10, Ph 11) by S-S bond scission.

The NHC‐stabilized C–F activation product [Ni(iPr2Im)2(F)(C6F5)] (1) was isolated from the reaction of [Ni(cod)2] with 1,3‐diisopropylimidazol‐2‐ylidene (iPr2Im) and hexafluorobenzene. Square‐planar (pentafluorophenyl)nickel complexes of the type [Ni(iPr2Im)2(X)(C6F5)] were obtained by a systematic derivatization of 1. The reaction of 1 with silylated compounds and organyllithium compounds led smoothly to replacement of the fluorido ligand in 1 by halogenido, trifluoromethanesulfonato, cyanido, organyl, selenolato, thiolato, and hydrido ligands. According to these procedures, the NHC‐stabilized (pentafluorophenyl)nickel complexes [Ni(iPr2Im)2(X)(C6F5)] (X = Cl 2, I 3, CF3SO3 4, CN 5), [Ni(iPr2Im)2(R)(C6F5)] (R = Me 6, Ph 7, C2Ph 8, η1‐Cp 9), [Ni(iPr2Im)2(SR)(C6F5)] (R = Ph 10, nPr 11), [Ni(iPr2Im)2(SeR)(C6F5)] (R = Ph 12, iPr 13), and [Ni(iPr2Im)2(H)(C6F5)] (14) were prepared. The complexes 4, 6. 9, 11, 13 and 14 were structurally characterized.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)