Efficient nickel mediated carbon–carbon bond cleavage of organonitriles

Abstract

The reactions of the nickel complex [Ni(2)(iPr(2)Im)4(COD)] 1 with organonitriles smoothly and irreversibly proceed via intermediates with eta(2)-coordinated organonitrile ligands such as [Ni(iPr(2)Im)2(eta(2)-(CN)-PhCN)] 2 and [Ni(iPr(2)Im)2(eta(2)-(CN)-pTolCN)] 4 to yield aryl cyanide complexes of the type trans-[Ni(iPr(2)Im)2(CN)(Ar)] (Ar = Ph 3, pTol 5, 4-CF(3)C(6)H(4) 6, 2,4-(OMe)2C(6)H(3) 7, 2-C(4)H(3)O 8, 2-C(5)H(4)N 9). The compounds 3, 7, 9 and have been structurally characterized. For the conversion of 2 to 3 a free activation enthalpy DeltaG++(328 K) of 103.47 +/- 0.79 kJ mol(-1) was calculated from time dependent NMR spectroscopy. The analogous reaction of arylnitriles with electron releasing substituents or heteroaromatic organonitriles is significantly faster compared to the reaction with benzonitrile or toluonitrile. The reactions of 1 with acetonitrile or trimethylsilyl cyanide afforded [Ni(iPr(2)Im)2(CN)(Me)] 10 and structurally characterized [Ni(iPr(2)Im)2(CN)(SiMe(3))] 11. The usage of an organonitrile with a longer alkyl chain, adiponitrile, yielded [Ni(iPr(2)Im)2(eta(2)-(CN)-NCC(4)H(8)CN)] 12 as well as the C-CN activation product [Ni(iPr(2)Im)2(CN)(C(4)H(8)CN)]13 in thermal and photochemical reactions, although this pathway seems to be significantly interfered with by decomposition pathways under the formation of the dicyanide complex [Ni(iPr(2)Im)(2)(CN)(2)] 14.