Kyle G Pearce, Agustín Morales, Michael S Hill, Claire L McMullin
The calcium hydride, [(BDI)CaH]2 (BDI = HC{C(Me)NDipp}2, where Dipp = 2,6-i-Pr2C6H3), reacts with Znt-Bu2 to form the monomeric and toluene-stabilised calcium dialkyl(hydrido)zincate, [(BDI)Ca-μ-H-Zn(t-Bu)2(η6-C7H8)]. When treated with dialkyl ethers, this compound initiates a sequence of twofold ether deprotonation and dealkylation by alkene extrusion, from which the resultant oxide dianion is sequestered as a tert-butoxide anion. Through a combination of experiment and theory, this completely selective C─O bond forming process is deduced to result from the formation of incipient calcium tert-butyl and hydride intermediates, and subsequent tertiary carbenium ion generation enabled by reduction of Zn(II) to elemental zinc. The overall transformation, therefore, may be rationalised as a consequence of latent extreme basicity in harness with a cooperative redox process that is intrinsic to the combination of dissimilar constituent metals.