The crystal and molecular structures of high-spin tris(1-pyrrolidinecarbodithioato)iron(III)(I){[Fe(CS2玭[CH2]4)3], 娳00 K, solid) 5繠B.M.}, and the predominantly low-spin tris(N-methyl-N-phenyldithiocarbamato)-iron(III)(II){[Fe(CS2玍ePh)3], 娳00K, solid) 3簠B.M.} have been determined by single-crystal X-ray diffraction methods, using conventional Patterson-Fourier heavy-atom methods followed by block-diagonal least-squares refinement. Final conventional R values were 0米 [(I), 1346 reflections] and 0簹 [(II), 1014 reflections]. The compounds both crystallize in the monoclinic system with Z= 4 (I): a= 16粳 ᠰ簴, b= 14絳 ᠰ簲, c= 10粲 ᠰ簳 Ŭ = 90糠ᠰ細, space-group P21/n; (II): a= 25糱 ᠰ簵, b= 12繰 ᠰ簱, c= 9紸 ᠰ簳 Ŭ = 116粠ᠰ粰, space-group P21/a.Both molecules consist of three substantially planar dithiochelate ligands surrounding the central iron atom in an approximately D3 configuration. The angular FeS6 geometries are closely comparable but there is a large contraction in the Fe-S distance on passing from the high-spin to the low-spin configuration. In (I), the iron-sulphur distance ranges from 2糸(1) to 2紴(1)Ŭ whereas in (II), the range is 2粸(1)-2糳(1)Ů The remainder of the molecular dimensions are normal within the limits of experimental error.