Oxygenation of simple zinc alkyls: surprising dependence of product distributions on the alkyl substituents and the presence of water

Oxygenation reactions of dialkylzinc solutions have been investigated. Me2Zn reacts with oxygen in the absence of water to give the bis(heterocubane) [(MeZn)6Zn(OMe)8], whereas Et2Zn and iPr2Zn afford the mono(heterocubanes) [(RZn)4(OR)4]. In the presence of small amounts of water (added during or after the oxygenation) the product types are reversed for Me2Zn and Et2Zn giving [(MeZn)4(OMe)4] and [(EtZn)6Zn(OEt)8], while being retained for iPr2Zn (giving [(iPrZn)4(OiPr)4]). Full characterization of all products by NMR spectroscopy, mass spectrometry, and elemental analyses is provided, and crystal structures of [(EtZn)6Zn(OEt)8] and [(iPrZn)4(OiPr)4] are reported. A rationalization of the different reactivities is attempted on the basis of DFT-calculated energies of some key reactants.