[{SiN Dipp }MgNa] 2 : A Potent Molecular Reducing Agent.

The bimetallic species, [{SiN Dipp }MgNa] 2 [{SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; (Dipp = 2,6- i -Pr 2 C 6 H 3 )], 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 Dipp }Mg(OCPh 2 ) 2 ], however, illustrate that treatment with such reducible, but O -basic, species can also result in reactivity in which the metals provide independent reaction products. The notable E -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 Dipp ligand, providing insight into the previously observed lability of the bidentate dianion and its consequent proclivity toward macrocyclization.