The reactivity of complexes of nickel(0) and platinum(0) containing benzyne and related small-ring alkynes

The preparation and reactivities of cyclohexyne and aryne complexes of platinum(0) and nickel(0) are reviewed. These complexes undergo insertions with unsaturated molecules such as alkenes, alkynes, isocyanides, CO and CO2. In the case of the nickel-benzyne complexes, consecutive insertions are observed with alkynes, leading to substituted naphthalenes with good regioselectivities. A possible mechanism for these double insertions, based on a combination of steric and electronic factors, is discussed in detail.