The reactivity of CO2 and COS with divalent and trivalent organosamarium complexes has been investigated, (C5Me5)(2)Sm(THF)(2) reductively couples CO2 in THF at room temperature to form the oxalate complex, [(C5Me5)(2)Sm](2)(mu-eta(2):eta(2)-O2CCO2), 1, in > 90% yield. The metal centers in 1 are formally eight-coordinate, The reaction of COS with (C5Me5)(2)Sm(THF)(2) is more complicated and generates a disproportionation product, (C5Me5)(2)Sm(mu-eta(2):eta(1)-S2CO)Sm(C5Me5)(2)(THF), 2, which has one (C5Me5)(2)Sm unit involved in a four-membered SmSCS ring. while the other (C5Me5)(2)Sm unit is bound to THF and the oxygen of the S2CO ligand. CO2 reacts with [(C5Me5)(2)Sm](2)(mu-eta(1):eta(1)-N2Ph2) in > 90% yield to form the asymmetrical monoinsertion product. (C5Me5)(2)Sm[mu-eta(2):eta(1)-PhNN(CO2)Ph]Sm(C5Me5)(2)(THF), 3. One (C5Me5)(2)Sm unit is involved in a five-membered SmNNCO ring, and the other is attached to THF and the other oxygen originating from CO2. 1-3 were characterized by analytical methods, X-ray diffraction, and NMR and IR spectroscopy.