Reduction of Hexaazatrinaphthylenes by Masked Divalent Lanthanide Dinitrogen Reagents.

The oxidation state +2 is of interest in rare-earth chemistry since it allows these conventionally redox-inactive metals to be used as reducing agents. However, the divalent oxidation state is difficult to form for most rare-earth elements, and the ensuing compounds are often unstable. Here, we describe an approach to rare-earth reduction chemistry that circumvents the divalent oxidation state by using compounds of trivalent rare earths that store reducing electrons on the dinitrogen ligand [N], akin to "masked" divalent reactivity. Thus, the dinitrogen complexes (, M = Y, Gd, Tb, Dy, Cp = 1,2,4-CBuH) reduce hexaazatrinaphthylene and its hexamethyl derivative to give trimetallic , where the [RHAN] ligands (R = H, ; R = Me, ) form with = 1/2, and with elimination of N. The structures of and reveal that the -butyl substituents strongly influence the core geometry of these trimetallic complexes. Analysis of the magnetism and electronic structure of and identifies ferromagnetic metal-radical exchange, with coupling constants of = +2.87 cm and +3.07 cm, respectively (-2 formalism). The unusual ferromagnetic exchange is a consequence of charge transfer to the gadolinium 5d, 6s, and 6p orbitals from the radical ligands.