Varying Lewis\nAcidity, Covalency, and Halide Mobility\nto Govern Oxidative Addition Reactivity of Ni–Group 13 Bimetallic\nComplexes

We report two new Ni–group 13 pincer-type systems\n(Ni–Al\nand Ni–Ga) and describe the influence of Lewis acidity, covalency,\nand halide mobility on the oxidative addition reactivity toward unsubstituted\naryl halides. Despite similar Lewis acidities of the Al- and Ga-based\nmetalloligands, the Ni–Ga pairing exhibits a significantly\nreduced effective Lewis acidity toward triethylphosphine oxide, supported\nby the greater Ni–Ga covalency as determined by density functional\ntheory. The higher effective Lewis acidity of Al in the Ni–Al\ncomplex and halide mobility are required to construct the key three-membered\nNi–X–Al poised-metallacycle, an intermediate in the\noxidative addition of unsubstituted aryl halides. The Al center further\nstabilizes the resulting Ni(II)–aryl product via a bridging\nhalide, thereby eschewing common decomposition pathways to Ni(I) byproducts.