Influence of Identity and Position of Ligand Substituents on Tris(amido) Yttrium Complexes

Early transition metals have been reported to be effective C(sp 3 )-C(sp 3 ) cross-coupling catalysts when paired with tris(amido) redox-active ligands. We developed a series of ligands to probe the effects of radical-stabilizing groups and substituent position on yttrium tris(amido) complexes. We synthesized neutral yttrium complexes 1-Y–3-Y which were characterized via NMR spectroscopy, single-crystal X-ray crystallography, cyclic voltammetry, and UV–vis spectroscopy. Single electron-oxidized complexes 1-Y ox –3-Y ox, which are relevant catalytic intermediates, were also synthesized and characterized via NMR, EPR, and UV–vis/NIR spectroscopy. DFT calculations were used to further elucidate the electronic structures of 1-Y–3-Y and 1-Y ox –3-Y ox . Complexes 1-Y–3-Y were used as catalysts in a C(sp 3 )-C(sp 3 ) cross-coupling reaction, and initial rates were used to determine the influence of the substituents on catalysis. The results indicate that substituent identity and placement impact the electronic structure of the complexes but have minor effects on catalysis.