Activation of Dioxygen via Neodymium-Alkali Metal Clusters

High Resolution Image Download MS PowerPoint Slide The discovery of new dioxygen binding and activation modes is of paramount importance in biological and synthetic systems. Herein, we describe two rare earth-alkali metal clusters displaying unusual reactivity with dioxygen. We isolate a trans -end-on peroxo dineodymium tetrapotassium species, (LH 4 Nd) 2 ( trans -μ-η 1:η 1 -O 2 )K 4 (thf) 4 ( 5 ), from reduction reactions of LH 5 Nd ( 1 ) and K[LH 4 Nd] ( 2 ) employing KC 8 in dry O 2 . Cluster 5 contains the first end-on peroxo coordination to an f-block metal. Surprisingly, when the weaker reductant sodium naphthalenide (Na[C 10 H 8 ]) is used, we isolate the cluster (LH 4 Nd) 2 (μ 6 -O)Na 4 (thf) 4 ( 6 ), indicating dioxygen’s O–O bond has been cleaved. The typically weak π-backbonding interaction of 4f-block elements to stabilize the end-on binding mode of O 2 is realized in 5 through a Lewis acid-assisted support of the peroxo species. Cleaving of the O–O bond in 6 is attributed to an increased Lewis acid effect rather than a larger chemical potential driving force since | E red (KC 8 )| > | E red ([C 10 H 8 ] − |. Lanthanide oxos are highly reactive; however, the oxo reactivity in 6 is tamed by dimerization and protection with four equatorial closely associated Na ions. This work demonstrates a synergistic effect between the rare earth and alkali metals in the binding and activation of dioxygen and provides a novel route to examine lanthanide peroxo/oxo chemistry.