Deep-blue solutions of Y2+ formed from Y(NR2)(3) (R = SiMe3) and excess potassium in the presence of 18-crown-6 at -45 degrees C under vacuum in diethyl ether react with CO at -78 degrees C to form colorless crystals of the (CO)(1-) radical complex, {[(R2N)(3)Y(mu-CO)(2)][K-2(18-crown-6)(2)])}(r nu) 1. The polymeric structure contains trigonal bipyramidal [(R2N)(3)Y(mu-CO)(2)](2-) units with axial (CO)(1-) ligands linked by [K-2(18-crown-6)(2)](2+) dications. Byproducts such as the ynediolate, [(R2N)(3)Y](2)(mu-OC CO){[K(18-crown-6)](2)(18-crown-6)}, 2, in which two (CO)(1-) anions are coupled to form (OC CO)(2-), and the insertion/rearrangement product, {(R2N)(2)Y[OC(=CH2)Si(Me-2)NSiMe3]}[K(18-crown-6)], 3, 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 2, the ynediolate [(R2N)(3)Y](2)(mu-OC CO)[K(18-crown-6)(THF)(2)](2), 2a, CO2 reacts analogously with Y2+ to form the (CO2)(1-) radical complex, {[(R2N)(3)Y(mu-CO2)(2)][K-2(18-crown-6)(2)]}(n), 4, that has a structure similar to that of 1. Analogous (CO)(1-) and (OC CO)(2-) complexes of lutetium were isolated using Lu(NR2)(3)/K/18-crown-6: {[(R2N)(3)Lu(mu-CO)(2)][K-2(18-crown-6)(2)]}(n), 5, [(R2N)(3)Lu](2)(mu-OC CO){[K(18-crown-6)](2)(18-crown-6)}, 6, and [(R2N)(3)Lu](2)(mu-OC CO)[K(18-crown-6)-(Et2O)(2)](2), 6a.