Isolation of (CO)<sup>1–</sup> and (CO<sub>2</sub>)<sup>1–</sup> Radical Complexes of Rare Earths via Ln(NR<sub>2</sub>)<sub>3</sub>/K Reduction and [K<sub>2</sub>(18-crown-6)<sub>2</sub>]<sup>2+</sup> Oligomerization

Deep-blue solutions of Y<sup>2+</sup> formed from Y­(NR<sub>2</sub>)<sub>3</sub> (R = SiMe<sub>3</sub>) and excess potassium in the presence of 18-crown-6 at −45 °C under vacuum in diethyl ether react with CO at −78 °C to form colorless crystals of the (CO)<sup>1–</sup> radical complex, {[(R<sub>2</sub>N)<sub>3</sub>Y­(μ-CO)<sub>2</sub>]­[K<sub>2</sub>(18-crown-6)<sub>2</sub>]}<sub><i>n</i></sub>, <b>1</b>. The polymeric structure contains trigonal bipyramidal [(R<sub>2</sub>N)<sub>3</sub>Y­(μ-CO)<sub>2</sub>]<sup>2–</sup> units with axial (CO)<sup>1–</sup> ligands linked by [K<sub>2</sub>(18-crown-6)<sub>2</sub>]<sup>2+</sup> dications. Byproducts such as the ynediolate, [(R<sub>2</sub>N)<sub>3</sub>Y]<sub>2</sub>(μ-OCCO)­{[K­(18-crown-6)]<sub>2</sub>(18-crown-6)}, <b>2</b>, in which two (CO)<sup>1–</sup> anions are coupled to form (OCCO)<sup>2–</sup>, and the insertion/rearrangement product, {(R<sub>2</sub>N)<sub>2</sub>Y­[OC­(CH<sub>2</sub>)­Si­(Me<sub>2</sub>)­NSiMe<sub>3</sub>]}­[K­(18-crown-6)], <b>3</b>, are common in these reactions that give variable results depending on the specific reaction conditions. The CO reduction in the presence of THF forms a solvated variant of <b>2</b>, the ynediolate [(R<sub>2</sub>N)<sub>3</sub>Y]<sub>2</sub>(μ-OCCO)­[K­(18-crown-6)­(THF)<sub>2</sub>]<sub>2</sub>, <b>2a</b>. CO<sub>2</sub> reacts analogously with Y<sup>2+</sup> to form the (CO<sub>2</sub>)<sup>1–</sup> radical complex, {[(R<sub>2</sub>N)<sub>3</sub>Y­(μ-CO<sub>2</sub>)<sub>2</sub>]­[K<sub>2</sub>(18-crown-6)<sub>2</sub>]}<sub><i>n</i></sub>, <b>4</b>, that has a structure similar to that of <b>1</b>. Analogous (CO)<sup>1–</sup> and (OCCO)<sup>2–</sup> complexes of lutetium were isolated using Lu­(NR<sub>2</sub>)<sub>3</sub>/K/18-crown-6: {[(R<sub>2</sub>N)<sub>3</sub>Lu­(μ-CO)<sub>2</sub>]­[K<sub>2</sub>(18-crown-6)<sub>2</sub>]}<sub><i>n</i></sub>, <b>5</b>, [(R<sub>2</sub>N)<sub>3</sub>Lu]<sub>2</sub>(μ-OCCO)­{[K­(18-crown-6)]<sub>2</sub>(18-crown-6)}, <b>6</b>, and [(R<sub>2</sub>N)<sub>3</sub>Lu]<sub>2</sub>(μ-OCCO)­[K­(18-crown-6)­(Et<sub>2</sub>O)<sub>2</sub>]<sub>2</sub>, <b>6a</b>.