Metal unsaturation and ligand hemilability in Suzuki coupling.

The combinative and complementary use of a hemilabile difunctional ligand on a metal, notably palladium, that is coordinatively and electronically unsaturated has led to the isolation of a string of unexpected low-valent complexes that are structurally intriguing. The ligands of interest are primarily ferrocenes functionalized by [P,N] and [P,O] donors. The characterization of these active Suzuki catalysts, which support sp(2)-sp(2) couplings, give valuable insights into the key Suzuki intermediates such as those arising from the reductive elimination, transmetallation, and oxidative addition steps. In this Account, we shall review and discuss our recent results in relation to selected developments in other laboratories.