LAUSR

Reaction of the readily reduced pincer ligand bis-tetrazinylpyridine, btzp, with the zerovalent metal source M(CO)3(MeCN)3 yields M(btzp)2 for M = Cr, Mo. These diamagnetic molecules show intrapincer bond lengths consistent with major charge transfer from metal to ligand, a result which is further supported by X-ray photoelectron spectroscopy. These molecules show up to five reversible outer-sphere electron transfers by cyclic voltammetry. The electronic structure of neutral M(btzp)2 is analyzed by DFT and CASSCF calculations, which reveal the degree of back-donation from the metal into pincer π* orbitals and also subtle differences in metal-ligand interaction for Mo vs Cr. Near-IR absorptions exhibited by both M(btzp)2 species originate from charge transfer among differently reduced tetrazine rings, which thus further support pincer reduction in these species.