Nickel promoted C-H, C-C and C-O bond activation in solution

Reaction of Nil(2) with the PCP-ligand {1-Et-2,6-((CH2PPr2)-Pr-/)(2)-C6H3} (1) results in selective activation of the strong sp(2)-sp(3) arylethyl bond to afford the aryl-nickel complex [Ni{2,6-((CH2PPr2)-Pr-i)(2)-C6H3}I] (2), whereas reaction of Nil(2) with {1,3,5-(CH3)(3)-2,6((CH2PPr2)-Pr-i)(2)-C6H} (4) leads to the formation of the benzylic complex [Ni{1-CH2-2,6-((CH2PPr2)-Pr-i)(2)-3,5-(CH3)(2)-C6H}I] (5) by selective C-H bond activation. Thermolysis of 5 results in formation of [Ni{2,6-((CH2PPr2)-Pr-i)(2)-3,5-(CH3)(2)-C6H}I] (6) by activation of the sp(2)-sp(3) C-C bond. The identity of the new 16-electron complexes 2 and 6 was confirmed by reaction of NiI2 with {1,3-((CH2PPr2)-Pr-i)(2)-C6H4 (3) and 11,3-(CH3)(2)-4,6-((CH2PPr2)-Pr-i)(2)-C6H2) (7), respectively, lacking the aryl-alkyl groups between the "phosphines arms" (alkyl = ethyl, methyl). Complexes 2 and 5 have been fully characterized by X-ray analysis. Nickel-based activation of an unstrained C-O single bond was observed as well. Reaction of the aryl-methoxy bisphosphine {1-OMe-2,6(CH2-(PPr2)-Pr-i)-C6H3 (8) with NiI2 results in the formation of the phenoxy complex [Ni{1-O-2,6-((CH2PPr2)-Pr-i)(2)-C6H3}I] (9) by selective sp(3)sp(3) C-O bond activation. (C) 2004 Elsevier B.V. All rights reserved.