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

Abstract

Reaction of NiI2 with the PCP-ligand {1-Et-2,6-(CH2PiPr2)2-C6H3} (1) results in selective activation of the strong sp2–sp3 aryl–ethyl bond to afford the aryl–nickel complex [Ni{2,6-(CH2PiPr2)2-C6H3}I] (2), whereas reaction of NiI2 with {1,3,5-(CH3)3-2,6-(CH2PiPr2)2-C6H} (4) leads to the formation of the benzylic complex [Ni{1-CH2-2,6-(CH2PiPr2)2-3,5-(CH3)2-C6H}I] (5) by selective C–H bond activation. Thermolysis of 5 results in formation of [Ni{2,6-(CH2PiPr2)2-3,5-(CH3)2-C6H}I] (6) by activation of the sp2–sp3 C–C bond. The identity of the new 16-electron complexes 2 and 6 was confirmed by reaction of NiI2 with {1,3-(CH2PiPr2)2-C6H4} (3) and {1,3-(CH3)2-4,6-(CH2PiPr2)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-(CH2PiPr2)2-C6H3} (8) with NiI2 results in the formation of the phenoxy complex [Ni{1-O-2,6-(CH2PiPr2)2-C6H3}I] (9) by selective sp3–sp3 C–O bond activation.