[{SiN}MgNa]: A Potent Molecular Reducing Agent

The bimetallic species, [{SiN}MgNa] [{SiN} = {CHSiMeN(Dipp)}; (Dipp = 2,6--PrCH)], is shown to be a potent reducing agent, able to effect one- or two-electron reduction of either dioxygen, TEMPO, anthracene, benzophenone, or diphenylacetylene. In most cases, the bimetallic reaction products imply that the dissimilar alkaline metal centers react with a level of cooperativity. EPR analysis of the benzophenone-derived reaction and the concurrent isolation of [{SiN}Mg(OCPh)], however, illustrate that treatment with such reducible, but -basic, species can also result in reactivity in which the metals provide independent reaction products. The notable -stereochemistry of the diphenylacetylene reduction product prompted a computational investigation of the PhC≡CPh addition. This analysis invokes a series of elementary steps that necessitate ring-opening via Mg → Na amido group migration of the SiN ligand, providing insight into the previously observed lability of the bidentate dianion and its consequent proclivity toward macrocyclization.