Treatment of metallic samarium with cyclooctatetracne in the presence of an equimolar amount of diaryl disulfide afforded mononuclear cyclooctatetraenyl(thiolato)samarium(III) complexes of the formula ( η 8-C 8H 8)Sm(SR)L x ( 3a: R=2-pyridyl, L=THF, x=0.5; 3b: R=2-pyridyl, L=HMPA, x=2; 3c: R=2,4,6-triisopropylphenyl, L=HMPA, x=2; HMPA=hexamethylphosphoric triamide) in modest yields. These complexes have been characterized by 1H-NMR spectroscopy and elemental analysis together with X-ray analysis for 3b and 3c. The complex 3b has a pseudo square pyramidal and four-legged piano-stool geometry coordinated by a planar η 8-C 8H 8 ring, a chelating pyridine-2-thiolato ligand, and two HMPA ligands, while the complex 3c has three-legged piano-stool geometry comprised of a planar η 8-C 8H 8 ring, a thiolato ligand, and two HMPA ligands.