Preparation of Ni(cod)₂ Using Light as the Source of Energy

A convenient method to prepare Ni­(cod)2 from Ni­(acac)2 using light as the source of energy is reported. In the first step of this process, xanthone is reductively dimerized upon irradiation of solar or LED light in 2-propanol to form a vicinal diol possessing a highly sterically congested C–C bond. In the second step, a ketyl radical derived from the diol reacts with Ni­(acac)2, ultimately reducing nickel­(II) to nickel(0), which is bound by 1,5-cyclooctadiene (COD) to produce Ni­(cod)2. This new method obviates the need for hazardous reductants such as diisobutylaluminum hydride (DIBAH) and sodium.