Formation of Carbon−Carbon-Bonded Dimers in the Reduction of [CoIIsalophen] [salophen = N,N‘-o-Phenylenebis(salicylideneaminato)]: Their Reactivity with Electrophiles To Form Co−C Bonds

Abstract

The reduction of cobalt−Schiff base complexes has been explored as a function of the nature of the ligand. In the case of substituted salen complexes, reduction occurred at the metal with the formation of bifunctional Co(I)−Na complexes, while for salophen derivatives the reductive coupling of imino groups was observed. Such C−C bonds function as electron shuttles in chemical reductions. Reduction of [Co(MeOsalen)] (1) with Na metal in THF led to a monomeric [Co(MeOsalen)Na(THF)2] (2A) and a dimeric [{Co(MeOsalen)Na(THF)}2] (2B) compound. Compounds 2A and 2B exemplify a bifunctional acid−base system with both centers in close proximity. The analogous reduction of [Co(salophen)] (3) and [Co(MeOsalophen)] (5) led to dimeric cobalt(II) derivatives containing a bridging C−C bond across two units in [Co2(salophen)2Na2(THF)6] (4) and [Co2(MeOsalophen)2Na2(THF)4] (6), respectively. However, such cobalt(II) centers behave as cobalt(I), since the C−C bond provides a pair of electrons to the metal couple during the...